Poster communications

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PC01

A STUDY ON THE POLYMERIZATION OF ENERGETIC (2-NITRATOETHYL)OXIRANE PREPOLYMER

Y.G. CHEUN

Agency for Defense Development, Yuseong P.O.Box 35-5, Daejeon, 305-600, Republic of Korea (e-mail: ygcheun / add.re.kr)

We synthesized energetic prepolymer(2-nitrato ethyl oxirane, NEO) for plastic-bonded explosives and measured its thermodynamic parameters.

2-Nitrato ethyl oxirane(NEO) as a monomer was synthesized from 4-butene-ol, the first-step was preparation of 1-nitrato-3-butene and second-step was synthesized 2-nitrato-ethyl oxirane from 1-nitrato-3-butene and then polymerized by cationic ring opening polymerization. The thermodynamic parameters were obtained from the ceiling temperature(Tc) values of 1 mole monomer at each reaction temperature. We varied feed rate of monomer, concentration of initiator and monomer to control molecular weight and polydispersity of perpolymer(NEO). The 1H-NMR spectrum prepolymer(NEO)(Fig.1) is consistent with a regular microstructure for exclusive ring opening at the C-O bond during polymerization. Number average molecular weight(Mn), polydispersity(PD), and glass transition of temperature(Tg), viscosity of prepolymer(NEO) were 2500, 1.07, -55oC and 300 poise respectively.

Scheme 1. Synthesis of 2-Nitratoethyloxirane (NEO)
Fig.1. 1H-NMR chart of Prepolymer(NEO) Fig.2. TGA chart of Prepolymer(NEO)

PC02

STUDY OF NETWORK FORMATION IN N-ISOPROPYLACRYLAMIDE GELS USING FLUORESCENCE TECHNIQUE

D. KAYAa , Ö. PEKCANa
aDepartment of Physics, Istanbul Technical University, Maslak,34469 Istanbul, Turkey (demet / itu.edu.tr)

The steady state fluorescence (SSF) technique was used to study the sol-gel transition for the solution free radical crosslinking polymerization of N-isopropyl acrylamide (NIPA), with N, N¢- methylenebis (acrylamide) (BIS) as crosslinker in the presence of ammonium persulfate (APS) as an initiator. Pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt, HPTS) used as a floroprobe for monitoring the polymerization. Pyranine molecules start to bind to NIPA polymer chains upon the initiation of the polymerization, thus the spectra of the bonded pyranines shift to the shorter wavelengths. The gel fraction exponent b and the weight average degree of polymerization exponent agree best with the mean-field (Flory-Stockmayer) results near the gel point for various crosslinker contents.


PC03

Abstract not supplied


PC04

Abstract not supplied


PC05

PHASE SEPARATION IN MAIZE STARCH - GUAR GUM - WATER SYSTEMS

P. PTASZEK*, A. PTASZEK, M. GRZESIK

University of Agriculture, Faculty of Food Technology, 30-149 Krakow, ul. Balicka 122, (*ptaszekp / op.pl).

Polysaccharides can be used as food texture forming additives. Due to very complicated structure, they exhibit a lot of quite interesting rheological phenomena. Investigation of linear viscoelasticity is a valuable tool in obtaining informations about structure and relaxation processes in biopolymer materials.

The aim of present work was to study phase separation in maize starch-guar gum-water systems. The investigations were performed using two techniques: rheological measurements in frequency domain and structural studies with AFM method. Interpretation of results was based on time-temperature superposition principle and phenomenological theory of viscoelasticity. Due to fact, that investigated system was thermal stable, it was allowed to apply time-temperature superposition principle. The values of parameter aT were calculated, that enables to create the master curves. Continuos Maxwell model was used to analyze phase separation in examined system. Obtained by Tikhonov regularization method spectra were heterogeneous, that proved non-homogenous structure of system.

Fig. 1: AFM phase image and stress relaxation spectra of guar gum-maize starch water system.

This work is supported by the Polish Scientific Committee grant no. 2 PO6T 082 27


PC06

INTERACTION OF HYDROCOLLOID NETWORKS WITH MONO- AND OLIGOSACCHARIDES

P. PTASZEK*, M. ŁUKASIEWICZ, B. ACHREMOWICZ, M. GRZESIK

University of Agriculture, Faculty of Food Technology, 30-149 Krakow, ul. Balicka 122, (*ptaszekp / op.pl).

Mono- and oligosaccharides plays an important role as an integral ingredients of different food systems. From the other hand such polymeric carbohydrates as starch or hydrocolloids serve as both the basic matrix of food or specific additives resposible for texture, thickening or many others properties of the product.

Polymers in solutions in many cases could be able to form networks with different origins in which the low molecular substances could take an important role.

Presented research covered the investigation on the interaction of basic mono- (a-D-glucose, D-Fructose) and oligosaccharides (sucrose) with one of the most commercially used hydrocolloid i.e. guar gum. As a basic model the 50%w/w water solution of the appropriate simple carbohydrate was chosen and the amount of guar was estimated on the level of 1%w/w. The viscoelastic measurements in frequency domain were carried out in RS-150 Rheometer (Haake) at different temperatures. The analysis covered the time temperature superposition method and fitting the continues Maxwell model to the experimental data.

As a conclusion it is worth to pointed out that the type of arising network strongly depends on the low molecular carbohydrate. The influence of temperature is also an important factor.

Fig 1. Stress relaxation spectra of 1% guar gum with different monosaccharides


PC07

MODIFICATION OF CHITOSAN GEL TO ENHANCE AND CONTROL FERTILIZER PERFORMANCE

M.H.M.HUSSAIN

Egyptian Petroleum Research Institute, Nasr City, Cairo, Egypt (mhmh43 / hotmail.com)

Polyacrylamid (PAAm) polyvinyl alcohol, starch hydrogels was chemically prepared. Chitosan derivatives gel product was prepared from Egyptian sea food wastes. then olegomers was prepared to formulate a novel smart hydro gels with super absorbing properties. The swelling of the super absorbing chitosanase hydro gels as well the fertilizer slow release proparities of the chitosan coating was studied. The swelling variations were explained according to swelling theory based on the hydro gel chemical structure.

Super absorbency, the slow release property of the chitosan-based hydro gel was investigated.

A tailor made super fertilizer (SF) was prepared to fit the requirements of the natural agriculture purposes.


PC08

STRUCTURAL CHANGES OF WATER SOLUTIONS OF POLYSACCHARIDES UNDER SHEAR FLOW

A. PTASZEK*, P. PTASZEK, W. BERSKI, M. GRZESIK

University of Agriculture, Faculty of Food Technology, 30-149 Krakow, ul. Balicka 122, (*annaptaszek / op.pl)

Thixotropy, attributed to the structure breakdown under shear stress, plays a significant role in thermal processing and mixing. In the present work, an attempt has been made to study the interactions of biopolymers networks, native maize and oat starches and their mixtures with selected hydrocolloids, in water solutions.

The rheological characteristics of biopolymer networks have been studied using a Cheng and Evans structural theory. The viscosity changes were described using structural parameter l included time-dependent effect:

.

The non-newtonian viscosity was given by a multiple exponential-type flow equation:

,

which parameters were calculated by regularisation method. The time changes of structural parameter were corresponded to biopolymers network behaviour. Connection of structural parameter l with viscosity allowed to describe the adaptability of networks to flow conditions.

Fig. 1: AFM image of native maize starch and xanthan water system and initial viscosity as a function of shear rate.


PC09

Carboxymethylcellulose/polyaniline blends. Synthesis and Properties

M. Lukasiewicz*, A. Ptaszek, L. Koziel, B. Achremowicz, M. Grzesik

Departament of Food Technology, Cracow Academy of Agricultural, ul. Balicka 122, PL-30-149 Krakow, Poland, tel. +48 12 662 47 70 *e-mail rrlukasi / cyf-kr.edu.pl

Polyaniline (PANI) as a one of the conducting polymers focuses an intensive research on both scientific and practical field. There is a quite a lot of known hybrid materials of PANI and other polymeric systems which applies different synthetic polymers what results in blends varying in their properties.

The presented research covers the synthesis of blends of polyaniline and semi-synthetic carboxymethyl cellulose (CMC). The obtained material could lead to a new anitelectrostatic material with interesting properties and hopefully seems to be applicable as an additive for packaging in both food and non-food industry.

The final material was obtained using both protonated (HCl) and deprotonated form of polyaniline in its semi-oxidized form of leucoemeraldine. Blending process was carried out by obtaining of thin layer by slow evaporation of the solvent from the mixture of PANI and CMC. After drying out, the material was characterized using typical analytic and spectroscopic methods. For the main investigation Atomic Force Microscopy (AFM) in non-contact mode was used what gave the information about the topology of the surface and also some structural information about the material.

The described process seems to be very interesting as a route for obtaining a new hybrid natural/synthetic material looking very interesting properties and a potential for application.

Fig. 1 Non-contact mode AFM scan of PANI/CMC blend.


PC10

PEROXIDATION OF INTERFACIAL SURFACE OF COLLOID SYSTEMS FOR CREATION OF NANOCOMPOSITES

І.А. МISKOVA, N.YU. SOLOMKO, О.G. BUDISHEVSKA, S.A. VORONOV

aInstitute of chemistry and chemical technologies, National university "Lvivska polytechnika", str. Bandery 12, Lviv, 79013, Ukraine (solomko_nadia / rambler.ru)

The filled polymers, polymeric dispersions and also polymeric mixtures are typical colloid systems with high-effective interfacial surface. The structure of interfacial layers causes properties of such composite materials and latexes. The designing of interfacial layers in polymeric composites can be carried out with the help immobilization of peroxidic groups in structure of heterofunctional polymers-modifiers on interfacial surface. The creation of peroxide-containing nanolayers on interfacial surface allows to modify its by grafting "from" and "up to" a surface that improves properties of materials.

The purpose of work is the creation of peroxide-containing heterofunctional copolymers with primary-tertiary peroxidic groups on a basis of copolymers of octene-co-maleic anhydride (O-MA). Copolymer of octene-co-maleic anhydride-co-tert-butylperoxymethylmaleate (O-MA-TBPMM) obtained by acylation of tert-butylperoxymethanol by copolymer of octene-co-maleic anhydride at presence triethylamine.

The contents of links of maleic anhydride in binary copolymer of octene-co-maleic anhydride determined by back рH-metric titration. The contents of links of tert-butylperoxymethylmaleate in copolymers determined chromatographically by amount of products of complete decomposition of peroxidic fragment and confirmed by iodometry and thermogravimetry methods.

Obtained copolymers used for modification of planar polymeric surface of polyethyleneterephthalate (PETPH) and surface of dispersed particles of aqueously-polymethylmethacrylatic (PMMA) dispersions. The formation of covalently graft layer of heterofunctional copolymer on a surface PETPH was confirmed by change of surface energy.

Modification of surface of polymeric dispersed particles was carried out by means of thermostatting of adsorptively-unsaturated latex at the presence of 5 mass %of O-MA-TBPMM from PMMA at 333K. Is shown that grafting of layer O-MA-TBPMM is accompanied by replacement of low-molecular emulsifier and TSC grows in 2 times after modificationduring 480 minutes.


PC11

A STUDY ON POLYSTYRENE NETWORKS IN LINEAR POLYSTYRENE SOLUTIONS

D. Sakar, A. Sarac, O. Cankurtaran, F. Karaman

Yildiz Technical University, Department of Chemistry, 34220, Davutpasa Campus, Istanbul/Turkey

Polystyrene networks were synthesized by free radical polymerization of styrene in the presence of benzoyl peroxide (BPO) as an initiator, divinyl benzene as an crosslinker at 50°C in toluene under nitrogen atmosphere. Firstly, synthesized polystyrene networks were swollen in toluene in order to release uncrosslinked polystyrene chains. After, swollen polystyrene networks were put in linear polystyrene solutions in toluene at different concentrations. The linear polystyrene samples were almost monodispers and with high molecular weight. The equilibrium swelling results were evaluated by means of Flory-Rehner theory. The Flory - Huggins polymer-polymer interaction parameters, c23 of network and linear polystyrene were negative, in contrast with the general result for isotropic mixtures. The extrapolated values of c23 to the zero solvent concentration were compared to the values reported for polystyrene network with linear polystyrene in the literature1.

As well as, the swelling behaviors of the synthesized polystyrene networks were studied at different temperatures in ethyl acetate, methyl acetate, iso-butyl acetate, tert-butyl acetate, n-butyl acetate, n-propyl acetate, iso-propyl acetate and iso-amyl acetate. The equations that give the variation of the polymer-solvent interaction parameter, c12 with temperature obtained from the data of swelling experiments were compared to the data obtained from the data of gas chromatographic measurements.

References

1. Russ T., Brenn R., and Geoghegan M., Macromolecules 2003, 36,127-141


PC12

A STUDY ON SWELLING BEHAVIOR OF POLY (p-CHLOROSTYRENE) NETWORKS IN SOLUTIONS OF LINEAR POLY (p-CHLORO STYRENE)

O. CELİK, D. Sakar, O. Cankurtaran, F. Karaman

Yıldız Technical University, Department of Chemistry, 34220, Davutpasa Campus, Istanbul/Turkey

Poly (p-chlorostyrene)(PPCS) networks synthesized by free radical polymerization were swollen in toluene. After, swollen PPCS networks were put in linear poly (p-chlorostyrene) solutions in toluene at different concentrations. The relation between swelling ratio in volume, qv and the volume fraction of the linear polymer in solution, f was given graphically and Flory-Huggins polymer-polymer interaction parameter, c23 of cross-linked PPCS with linear PPCS was calculated. The equilibrium swelling data were evaluated by means of Flory - Rehner theory. Polymer-polymer interaction parameters, c23 of network and linear PPCS were negative, in contrast with the general result for isotropic mixtures. The extrapolated values of c23 to the zero solvent concentration were compared to the values reported for polystyrene network with linear polystyrene in the literature.

As well as, the swelling behaviors of the synthesized PPCS networks were studied at different temperatures in benzene, ethyl benzene, n-propyl benzene, isopropyl benzene, ethyl acetate and mixtures of toluene-methanol and toluene-acetone. The equations that give the variation of the polymer-solvent interaction parameter, c12 with temperature were obtained from the data of swelling experiments.

References

1. Russ T., Brenn R., and Geoghegan M., Macromolecules 2003, 36,127-141


PC13

DETECTING THE GEL POINT IN REVERSIBLE AND IRREVERSIBLE SYSTEMS: COMPARISON OF METHODS (DLS, RHEOLOGY AND NMR)

SVEN RICHTER1*, VOLODYMYR BOYKO1, ROLF MATZKER1, KLAUS SCHRÖTER2, TORSTEN BRAND3, STEFAN BERGER3

1Dresden University of Technology, Institute of Physical Chemistry and Electrochemistry, Mommsenstrasse 13, D-01062 Dresden, Germany, *e-mail: sven.richter / chemie.tu-dresden.de;
2Martin-Luther-University of Halle-Wittenberg, Department of Physics, Experimental Polymer Physics Group, Hoher Weg 8, D-06120 Halle (Saale), Germany;
3University of Leipzig, Institute of Analytical Chemistry, Linnéstrasse 3, D-04103 Leipzig, Germany.

The sol-gel transition of a radical chain cross-linking copolymerization system based on N-vinylcaprolactam has been studied by using in-situ time-resolved dynamic light scattering (DLS) and in-situ rheology.[1] A critical dynamical behavior was observed near the sol-gel transition, which is characterized by the presence of a power-law spectra over three decades in the time-intensity correlation function (TCF) g2(t)−1 ~ t−μ and over two decades in rheology experiment G'(ω) ~ G''(ω) ~ ωn.

DOI and ONUKI[2] discussed a power-law decay for the dynamic structure factor S(q,t) and the time-dependent modulus G(t), where both quantities follow the same power law exponent, i. e. g1(q,t) ~ S(q,t) ~ G(t) ~ t−β, with β = 0.2…0.4; μ = 2β. By FOURIER transformations, shear relaxation modulus G(t) and storage G'(ω) and loss parts G''(ω) of complex modulus are G(t)~ t−β ⇔ G'(ω) ~ G''(ω) ~ ωβ. That implies, that the critical exponents β and n have the same value at the gel point, n = β. But up to now, no experimental comparison was done. It was also pointed out, that the problem of comparison of the exponents μ (or β) and n is not settled at all.[3] The obtained critical exponents were μ ≈ 0.62 (β ≈ 0.31) and n ≈ 0.75.[1]

The gelation threshold of a thermoreversible gelling mixture made of xanthan gum and locust bean gum (in a weight ratio of 1:1) has been investigated by using DLS and rheology.[4] A critical dynamical behavior was also found at the gelation threshold, characterized by a power-law in the TCF g2(t)−1 ~ t−0.36 at 42°C and in the oscillatory shear experiment G'(ω) ~ G''(ω) ~ ω0.62 at 47°C. Please note the reproducible 5 K difference in the used two methods for the determination of the gel point!

In conclusion, one must be very careful in comparing the critical exponents obtained by rheology and DLS, and especially the used methods itself. It appears, that relations like n = β and n ≈ μ ≈ 2β are not fulfilled (at least for the investigated systems) within the experimental error bars.

Furthermore at the same system (but in D2O), a comparative monitoring using DLS and measuring the spin-lattice relaxation time T1 of several protons has been done.[5] At 48°C a power-law spectra in the TCF was observed. The increase in T1 with increasing temperature becomes steeper at 50°C indicating a significant change in the local mobility of one anomeric proton of the xanthan gum side chain and the anomeric protons of the locust bean gum mannose backbone.


PC14

NEW BIOSYNTHETIC CROSSLINKED HYALURONIC ACID FOR BIOMEDICAL APPLICATIONS

F. GUILLAUMIE, M. MELLERGAARD, M. BOYSEN, K. SCHWACH-ABDELLAOUI

Novozymes Biopolymer A/S, Krogshøvej 36, DK-2880 Bagsværd, Denmark (fagu / novozymes.com, www.novozymes.com )

Hyaluronic acid (HA) is a natural and linear carbohydrate polymer belonging to the class of the non-sulfated glycosaminoglycans. HA is composed of beta-1,3-N-acetyl glucosamine and beta-1,4-glucuronic acid repeating disaccharide units with a molecular weight up to 6 MDa. Hyaluronic acid is found in the vitreous body and is also abundant in the extracellular matrix, especially of soft connective tissue, and in the synovial fluids of articular joints. It exists in nature as a hydrated gel and is ubiquitous in human and animal tissues. HA influences cell behavior and exhibits important biological functions in the body. In the last decades, numerous applications in the cosmetic and biomedical fields including skin moisturizers, osteoarthritis treatment, ophthalmic surgery, rheumatology, adhesion prevention, tissue engineering and drug delivery have been proven and marketed owing to the distinctive visco-elastic properties of this biopolymer and its lack of immunogenicity or toxicity. However, in order to improve the physico-chemical properties and the biostability of HA and to create various physical forms (e.g. hydrogels, sponges, films, fibers, and microspheres) towards the fabrication of novel biomaterials, HA needs to be modified. A wide range of chemical modification methods have thus been implemented based on cross-linking and attachment of pendant groups.

In this work, we have cross-linked sodium hyaluronate produced by fermentation of a novel, superior and safe strain, namely Bacillus subtilis. Accordingly, the swelling behavior, the rheological properties as well as the biostability of the resulting hydrogels will be presented.


PC15

SYNTHESIS OF POLYURETHANE NETWORKS FROM RECYCLED POLYOLS

H. BENEŠa, M. DUŠKOVÁa, M. PEKÁREKa, J. KOVÁŘOVÁa,H. VALENTOVÁb

aInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám 2, CZ-162 06 Praha 6, Czech Republic (benesh / imc.cas.cz)
bDepartment of Macromolecular Physics, Faculty of Mathematics and Physics of Charles University, V Holešovičkách 2, CZ-182 00 Praha 8, Czech Republic

Nowadays, the most important method of chemical recycling of polyurethane (PUR) scrap is glycolysis involving reaction of PUR with diols at elevated temperature to produce liquid mixture of polyols. At present, the major part of recycled polyols is used for manufacture of rigid PUR foams. Nevertheless, it is challenging to look for a new application area for these recycled polyols.

We have studied the possibility of usage of recycled polyols from glycolysis of flexible PUR foam in synthesis of PUR networks. We tested two kinds of recycled polyols -from glycolysis with diethylene glycol (DEG) and dipropylene glycol (DPG) respectively, in reaction with trimer of hexamethylene diisocyanate (Desmodur DN 3300). Polyaddition reactions were carried out with initial molar ratio [NCO]/[OH] = 1/1, in 2-heptanone (methyl amyl ketone) as solvent, with catalyst (dibutyltin dilaurate- DBTDL) at room temperature.

The optimal reaction conditions for polyaddition reaction were determined- 80% solids, 200 ppm DBTDL at 25°C. Kinetic measurements were also conducted- critical conversions around 60 % were determined for all tested recycled polyols and different contents of solvent. Some kinetic experiments were carried out at elevated temperatures (30, 35 and 40°C) and reaction half-times 94 min (25°C), 86 min (30°C), 43 min (35°C) and 35 min (40 C) were calculated.

From thermogravimetric analysis follows that PUR network containing recycled polyols is thermally stable up to 200°C. Dynamic-mechanical-thermal analysis of PUR network was carried out on dry and equilibrium swollen samples. From swelling experiments content of gel and concentration of elastically active network chains (crosslinking density) of PUR network containing recyclate were determined.

The results show that recyclate from DPG glycolysis is more suitable for synthesis PUR networks and gives pale yellow transparent material. The great advantage of this synthesis is 100% replacement of virgin alcohols by recycled polyols while keeping excellent mechanical properties.


PC16

PREPARATION OF GEL WITH PIROXICAM USING ACRYLIC ACID POLYMERS

S. DOUALI, K. HAMMOUDI

LSP University of Boumerdes 35000 ALGERIA(sal_ham2004 / yahoo.fr)

The aim of this work had consisted of the formulation and the study of the development of a pharmaceutical gel containing "Piroxicam".

Several gel with various concentrations of gelling agents such as Carbopol, Carbomère, and the hydroxyethylcellulose(HEC) were formulated. The different formulations were then subjected to the rheology tests and to a quality control.

The results obtained are in conformity with the recommendations of the various Pharmacopeias. The excipients used at the time of the formulation of this gel are 95% ethanol, benzylic alcohol and the propylene glycol.

The macroscopic observations of the aspect and the study of the rheological parameters of the prepared gel with various concentrations by measuring viscosity according to the speed of shearing and by tracing each time the corresponding rheogram, made it possible to retain the preparation which is very close to the freezing of reference and which contains 0,4% of carbopol and 0,6% of HEC.

The separate use of Carbopol and HEC in formulations did not lead to convincing results. A study of one two months duration stability to 4, 25 and 35°C was performed. The recommendations ridges are to work at 25°Cwith a water content of 60%.


PC17

MODEL OF DIFFUSION OF AN ACTIVE SUBSTANCE FROM A POLYMER SYSTEM

K HAMMOUDIa, L LAMMOUDIb

a:Laboratory of Petrochemical Synthesis, University of Boumerdes, 35000-Algeria(k_hammoudi2000 / yahoo.fr),Tel/Fax: 21324816848.
b: Center of Research in Drugs, SAIDAL, El-Harrach, 16100, Algeria

The submicronic systems (nanoparticules, liposomes) arouse more and more interest in the transport of the drugs to their biological target.

The release of the active ingredient starting from a vectorized form remains always an objective concrèt.

The aim of this work consisted of the study of the release of Piroxicam starting from nanoparticules made up of Piroxicam, of Pluronic and the PLGA (lactic of and glycolic acid copolymer) in various biological environments. Only the plug medium (pH = 7) ended in better results.

To accelerate the release of the active ingredient, the nanoparticules were dispersed in ethanol and benzylic alcohol.

The quantity of Piroxicam released was determined by UV/Vis spectrophotometry at with 333nm. It reached 23% at the end of 10 days in the case of the use of two solvents.

But it was observed a very great variation of the release of the active ingredient according to the residence time in the medium of dissolution. Lastly, it is proven that the properties of diffusion or biological breakdown of polymer plays a part influencing the process of diffusion of the active ingredient starting from its polymeric matrix.


PC18

STUDY OF POLY(N,N-DIMETRHYLACRYLAMIDE) HYDROGELS AS HOSTS OF LANTHANIDE ION COMPLEXES.

V. BEKIARI*, P. LIANOS

bekiari / des.upatras.gr
Engineering Science Department, University of Patras, GR-26500 Patras, Greece

Poly(N,N-dimethylacrylamide) hydrogels can be used as hosts for terpyridine-lanthanide ion complexes. The polymer hydrogel can be obtained in three different phases: Swollen with a solvent, dried by Freeze-drying where it loses the solvent but preserves the Swollen configuration and dried in the air where it Shrinks. When solubilized in Swollen phase, ligand and ion are segregated. Then metal-centered emission can be obtained by energy transfer from excited ligand. In the Shrunk phase both agents are retained and a strong complex is formed between them. In that case, an intense green luminescence is emitted, which is ligand-centered and is independent of the complexed ion. In the absence of any ion, the ligand emits blue luminescence, independently of the polymer phase. If Europium (III) ions are used, then blue, green or red emission can be produced at appropriate compositions and polymer phases. In Fig.1 luminescence spectra of the Tpy-Eu3+-PDMAM system are presented: (1) Swelled with water or Freeze-dried and (2) Shrunk. Excitation wavelength. 380nm for both cases.

FIG.1

We thank the European Social Fund (ESF), Operational Program for Educational and Vocational Training II (EPEAEK II), and particularly the Program PYTHAGORAS II, for funding the above work.


PC19

EFFECT OF DILUENT ON CYCLIZATION AND MECHANICAL PROPERTIES OF POLYURETHANE NETWORKS

A. ĎURAČKOVÁa,b, H. VALENTOVÁc, M. DUŠKOVÁ-SMRČKOVÁa,c, K. DUŠEKa

aInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
bBata University Zlín, Czech Republic
cFaculty of Mathematics and Physics, Charles University, Prague, Czech Republic

In the majority of crosslinking systems, formation of intermolecular bonds is accompanied by formation of cycles. The addition of a diluent enhances cyclization and weakens interchain interactions. In this contribution, the extent of cyclization is characterized by shift of the critical conversion of functional groups to higher values with increasing dilution and decrease of equilibrium modulus of elasticity. The polyurethane networks were prepared from polycaprolactone diol (PCLD), polycaprolactone triol (PCLT) and a polyester tetrafunctional star crosslinked with a stoichiometrically equivalent amount triisocyanate (trimer of 1,6-diisocyanatohexane) and at various dilutions with diglyme. The gel point conversion, ag, decreases with the reciprocal initial concentration of functional groups, 1/c0. The slope of this dependence decreases with increasing molecular weight of the PCLT component due to longer topological distance of functional groups. The fraction of bonds lost in cycles at concentration of solids 60 %-wt. varied from 10 % for PCLD to 34 % for the tetrafunctional star. Equilibrium mechanical measurements in tension of dry and equilibrium swollen samples characterized the intensity of formation of elastically inactive cycles (IEC). The equilibrium modulus decreases with increasing dilution. For PCLT systems, the concentration of EANC's decreases by about a factor of 2 when passing from bulk samples to those diluted by 70% solvent. The shift of critical conversion expressed as ag-ag,id with ag-ag,id µ (j0)k, obeys a power law with exponent k = 0.41-0.37. For lowering of the reduced equilibrium modulus of swollen samples Ge(j2)1/3 µ (j0)e, the exponent e varies between e = 1.9 and 2.7. The decrease of modulus (corrected for different degree of swelling) is due to different network chain dimensions in dry state (factor (j0)2/3), enhancement of formation of elastically inactive cycles (IEC) (exponent s) and, possibly, decrease in the number of trapped entanglement by dilution at network formation (h» 2; if all factors are additive e » 2/3 + 2 + s). Since e - 2/3 » 1.2 - 2, and close to the gel point Ge(j2)1/3(j0)2/3 µ |ag-ag,id|3 and |ag-ag,id|3 µ (j0)1.2 (cf. the gel point measurements), the contribution by trapped entanglements seems to be unimportant.


PC20

Interpenetrating polymers network Hydrogels based on polyurethane

T.T. Alekseeva, L.A. Protasenya, N.V. Yarovaya, Yu.S. Lipatov

Institute of Macromolecular Chemistry, NAS of Ukraine, 02160 Kiev, Kharkovskoye Shausse, 48, Ukraine (lipatov / i.kiev.ua )

Hydrogels of interpenetrating polymers networks are important materials of both fundamental and technological interests. In particular, perspective hydrogels are based on hydrophilic, polymeric networks capable of imbibing large amounts of water or biological fluids. Changed chemical structure of hydrophilic networks can vary of their sensors properties in wide range. Varying of MM of polymeric segment between two network junction points reach different degree of the swelling dependent on temperature, the pH, ionic concentration and electric field.

Interpenetrating polymers networks hydrogels were obtained by the sequential curing based on crosslinked polyurethane (PU) with different MM of oligoether (polyethylene glycol MM 4500, 6000, 10000) and gelatin, or carboxymethylcellulose, or poly(2-hydroxyethyl methacrylate).

It was established, that degree of equilibrium of the swelling for PU and semi-IPNs increase with increasing of MM of oligoether. The effect of temperature on swelling behavior of initial PU and IPNs gels has been analyzed by variation from 20° to 60°С. The rate of the swelling increase for initial PU and semi-IPNs gels with increasing of the temperature, but degree of the swelling and time of maximum of the swelling decrease.

DSC method was used for determination parameters of temperature transitions for initial PU and IPNs gels and typical for nonfreezing and free water in hydrogels. The amount of free and nonfreezing water increased with increasing of MM of oligoether. Physical state and quantity of water in hydrogels show considerable influence on the selectivity and properties of IPNs hydrogels.


PC21

THE INTERACTION OF ANIONIC CROSSLINKED POLYELECTROLYTE GELS WITH ASCORBIC ACID

E. KARPUSHKIN, E.SBRUEVA, V. SKOBELEVA, A. ZEZIN

Chair of High-Molecular Compounds, Department of Chemistry, Moscow State University, 119992, Leninskie Gory, Bld. 3, Moscow, Russia

The interaction of ascorbic acid with bulk polyelectrolyte hydrogels based on sodium acrylate as well as sodium 2-acrylamido-2-methylpropanesulfonate copolymerized with various amounts of acrylamide in the presence of N,N'-methylenebisacrylamide was studied. We were the first to demonstrate that sulfonate-containing hydrogels are rather quickly destructed in the acidic aqueous media in the presence of ascorbic acid. Acrylate-based gels are not destructed at the same conditions; neither do non-ionic cross-linked polyacrylamide gels. Sulfonate-based gels are not destructed in the presence of sodium ascorbate at alkaline pH. Thus it may be thought that possibility of the interaction described should be governed by the ionization state of both components involved.

It is well known that ascorbic acid itself is unstable in the acidic aqueous media in the presence of oxygen. It was demonstrated that ascorbic acid aqueous solution stored long enough will not initiate sulfonate hydrogels destruction. Thus it is proved that only ascorbic acid itself or any of intermediate decay products may start gel degradation process.

Destruction kinetics was studied by means of measuring absorbance increase due to organic dye Rhodamine 6G previously adsorbed by a gel sample releasing from hygrogel upon its degradation. Induction period appeared to be characteristic of kinetic curves thus obtained. Induction time may be reduced up to zero if ascorbic acid solution stored for several hours is used for the experiment instead of prepared from ascorbic acid powder, the slope of the curve remaining almost unchanged. This result indicates that most likely gel destruction is due to the interaction of sulfonate-containing polyelectrolyte network with some ascorbic acid decay intermediate.

Gel degradation at various temperatures was studied. Temperature influences greatly the interaction under consideration: destruction time is reduced by almost 2 orders of magnitude when T is up by 35°, other conditions being equal. The induction period is changed as well as kinetic curve slope in the region of most intense sample degradation.

Degradation of gels with different ratios of ionic component was examined. The relative amount of charged groups has a great impact on interaction rate.

It may be judged that at least one of the gel degradation stages may be treated as polyelectrolyte interaction with a low-molecular ascorbic acid decay intermediate.


PC22

Effect of 3d structures on recycled pet/organoclay nanocomposites

M. Kráčalíka,b, M. Studenovskýa, J. Mikešováa, r. thomannb, ch. Friedrichb

aInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovský Sq. 2, CZ-162 06 Praha 6, Czech Republic (kracalik / imc.cas.cz)
bFreiburger Materialforschungszentrum, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Straße 21, D-79104 Freiburg, Germany

Formation of physical network in polymer nanocomposites leads to significant improvement of processing and utility properties of the filled materials. Dispersion of silicate platelets in PET by melt mixing depends on shear forces as well on surface chemical treatment of the filler.

In our work, the level of dispersion of clay layers in polymer matrix was determined by X-ray diffraction analysis and transmission electron microscopy. Melt rheology was used to examine the presence of network particles. It was shown that the addition of 5 wt. % of organomodified montmorillonite into recyclate leads to a 3D network structure manifesting itself by a secondary plateau of at lowest frequencies. Evaluation of XRD and TEM experiments supported the mentioned conclusion.


PC23

APPLICATION OF POROUS THREMOSENSITIVE GEL FOR DEWATERING OF ORGANIC SLURRY

T. GOTOH, S. SAKOHARA

Department of Chemical Engineering, Hiroshima University, Higashi-Hiroshima, Hiroshima739-8527, Japan( tgoto / hiroshima-u.ac.jp )

Solid materials in organic slurry discharged from food processing plants contain some useful components such as proteins, vitamins and enzymes. However, it is hard to recover thosematerials by mechanical dewatering without the aid ofchemicals. Wereported the preparation method of the supported thermosensitive porous gel and applied it for dewatering of rice rinsed water1). In this study, the effects of some modifications of the gel on dewatering capacity were investigated.

The porous NIPAM gels were prepared utilizing a phase separation and were supported by stainless net to improve its mechanical strength1). A desired amount of the slurry was put onto the gel, which was previously shrunk at 50°C. The slurry was dewatered at room temperature.

Figure 1 shows the effect of monomer concentration on dewatering rate.The water content of the slurry was decreased to about 50 wt % within 30minutes. The dewatering rate increased with increasing the monomer concentration, which was expected to increase the network concentration. The increased network concentration maintained high osmotic pressure of the gel for the dewatering.

1)T. Gotoh, H. Okamoto and S. Sakohara, J. Chem. Eng. Japan, 37, 347-352 (2004)

Fig. 1. Effect of monomer concentration on dewatering rate

PC24

CHEMORHEOLOGY OF EPOXY/ORGANOMODIFIED LAYERED SILICATE NANOCOMPOSITES

L. SOLAR, A. NOHALES, C.M. GOMEZ

Universitat de Valencia; Institut de Ciencia dels Materials (ICMUV); Dr Moliner, 50. 46100 Burjassot (Valencia) Spain. (lorena.solar / uv.es)

Nanocomposites based on organically modified layered silicates represent an area of research which has shown explosive growth in the past decade. Among these systems, thermoset polymer nanocomposites are beginning to receive considerable attention. In order to process thermosets it is an important point the control of the determinant steps of the cure process, i.e. gelation and vitrification. In this paper we have studied the network build-up of an epoxy matrix modified with an organoclay as a function of the cure temperature and the concentration of filler by rheology.

The layered silicate used in this study is Nanofil 919 supplied by Süd Chemie. It is a modified montmorillonite with an (CH3)2N+CH2PhHT where HT is 65% C18, 30% C16, 5% C14. A diglycidyl ether of bisphenol A (DGEBA) GY250 was used as epoxy resin. The curing agent was 4,4-methylene bis(2,6-diethyl aniline) (MDEA) supplied by Lonza. Stoichiometric mixtures of epoxy-amine were used. Isothermal rheological experiments were conducted on a TA AR-1000 rheometer using parallel plate mode. Differential scanning calorimetry (DSC) experiments were also carried out.

Representative isothermal cure plots (storage modulus versus time) with varying amounts of clay show a gradual increase in the modulus followed by a rapid increase at gelation and a levelling as vitrification occurs. The effect of the clays on the gel times can be seen by plotting the storage (G') and loss moduli (G") as a function of time. Evolution of the morphology during curing has been found to be dependent on the rate of intergallery diffusion of the prepolymer and subsequent gelation and vitrification, as well as the intra and extragallery cure kinetics. Gelation and vitrification times and activation energies for the nanocomposite systems were lower than that of the neat resins, indicating a catalytic effect of the clays on the curing reaction. Curing kinetics experiments performed on DSC confirm this phenomenon.

Acknowledgements: Financial support from projects MAT2002-03485 and GV04B133 is gratefully acknowledged.


PC25

gelation and network formation monitored by ultrasonic analysis

F. LIONETTO, A. SANNINO, G. COLUCCIA, A.MAFFEZZOLI

Department Engineering for Innovation, University of Lecce, via Monteroni 73100 Lecce, Italy. E-mail: alfonso.maffezzoli / unile.it

Ultrasonic waves are responsible of a dynamic mechanical deformation at very high frequencies on a material. Therefore an ultrasonic dynamic mechanical analysis (UDMA) can be set up to study chemical or physical changes occurring in a polymer. In particular, the evolution of an elastic modulus can be measured as a function of time and temperature. An apparatus developed in our laboratory (Fig.1) is applied to measure, in transmission mode, the ultrasonic properties of curing of thermosetting resins (epoxy and unsatured polyester), crosslinking of cellulose based hydrogels and physical gelation of waxy crude oil. It consists of two specifically developed ultrasonic transducers, fitted into the disposable tools of a parallel plate rheometer (Ares, Scientific Rheometric) and connected with a pulser-receiver card. This latter generates a pulse train, amplifies the signal transmitted through the sample and provides an analogue/digital conversion of the signal, that, using a dedicated software, is analyzed in order to obtain the velocity and attenuation of the ultrasonic wave. The longitudinal ultrasonic velocity and attenuation are related with the evolution of the complex longitudinal bulk modulus. The ultrasonic complex bulk longitudinal moduli obtained during hydrogel crosslinking and oil gelation are compared with low frequency complex shear moduli obtained by DMA. Simultaneous rheological and ultrasonic measurements have been also performed. A DSC analysis has been also carried out to compare the evolution of the degree of reaction of reactive resins with that of the ultrasonic modulus.

Fig. 1. Apparatus for Ultrasonic Dynamic Mechanical Analysis (UDMA)


PC26

RECOVERY OF PALLADIUM FROM SIMULATED SOLUTIONS USING SELECTIVE ION-EXCHANGE RESINS WITH S-DONOR ATOMS

Z. HUBICKIa,b, B. ŁODYGAa, A. ŁODYGAa, M. LESZCZYŃSKAb

a Fertilizer Research Institute, 24-100 Puławy, Poland
b Department of Inorganic Chemistry, Faculty of Chemistry, Maria Curie-Sklodowska University, Maria C. Sklodowska Sq.2, 20-031 Lublin, Poland (hubicki / hermes.umcs.lublin.pl)

Ion-exchange separations of palladium, platinum, rhodium and iridium ions were most frequently based on application of anion exchangers in chloride solutions making use of the change of valency value till a proper distribution coefficient was reached. Recently, very good results have been obtained in both sorption and separation of trace and milligram amounts of noble metal ions using chelating ion exchangers. They are characterized by high capacity and selectivity for precious metal ions, fast kinetics, high mechanical strengths and toughness of the exchanger particles. Their properties depend on the type of functional groups, though to a lesser extent on grain size and physical properties. Based on the hard and soft acids and bases theory (HSAB), the ion exchangers of the functional groups containing S donor atoms interact strongly with the soft acids like precious metal ions. This condition is satisfied by palladium(II) ions. Numerous chelating resins selective for palladium (II) ions are known.

The paper discusses applicability of selective ion exchangers of functional thiol and thiourea groups in removal of Pd(II) ions from the model solutions of the composition: 0.1÷6.0 M HCl - 0.0011 M Pd(II), 0.1 ÷ 0.9 M HCl - 0.9 ÷ 0.1M HNO3 - 0.0011M Pd(II), 1.0 M MClx - 0.1 M HCl - 0.0011M Pd(II) (where MClx= AlCl3, ZnCl2, CuCl2, NiCl2). Polystyrene ion exchangers of macroporous structure of the commercial name Duolite GT-73 and Lewatit TP-214 were investigated. Weight and bed distribution coefficients as well as recovery factors of Pd(II) were determined. Moreover, working and total ion exchange capacities were estimated. The effect of acid concentrations, macrocomponent addition as well as ion exchanger - solution contact time on sorption was studied.


PC27

PRECONCENTRATION OF Pd(II) TRACES ON CHELATING AMIDOXIME, AMINOPHOSPHONIC AND IMINODIACETATE ION EXCHANGERS

Z. HUBICKIa,b, M. LESZCZYŃSKAb B. ŁODYGAa, A. ŁODYGAa,

a Fertilizer Research Institute, 24-100 Puławy, Poland
b Department of Inorganic Chemistry, Faculty of Chemistry, Maria Curie-Sklodowska University, Maria C. Sklodowska Sq.2, 20-031 Lublin, Poland (hubicki / hermes.umcs.lublin.pl)

Although the platinum group elements belong to those with the smallest abundance in the earth crust, they are the object of high scientific and public interest. Most of palladium produced is consumed in catalysts, chemical, dental, electrical, petrol and jewellery industries.

Noble metals recovery from waste solutions is a very important economical and ecological problem attracting attention of many researchers. Polymeric materials and ion-exchange resins containing selective functional groups have been used for many years in hydrometallurgy processes.

The paper presents selective removal of Pd(II) ions from the following model systems: 0.1÷6.0 M HCl - 0.0011 M Pd(II), 0.1 ÷ 0.9 M HCl - 0.9 ÷ 0.1M HNO3 - 0.0011M Pd(II), 1.0 M MClx - 0.1 M HCl - 0.0011M Pd(II) (where MClx= AlCl3, CuCl2, NiCl2) on the chelating ion exchangers. The influence of acid concentration, phase contact time as well as macrocomponent addition on Pd(II) ions sorption was studied. The total capacities and recovery factors of Pd(II) ions were determined by the batch method. As follows from the results, the ion exchangers of amidoxime and iminodiacetate functional groups can be widely recommended for Pd(II) ions removal from anodic slimes, used up catalysts as well as trace analysis because of high selectivity.


PC28

APPLICATION OF GEL AND MACROPOROUS ION-EXCHANGE RESINS IN Pd(II) IONS SORPTION FROM MODEL CHLORIDE SOLUTIONS

Z. HUBICKIa,b, M. LESZCZYŃSKAa

a Department of Inorganic Chemistry, Faculty of Chemistry, Maria Curie-Sklodowska University, Maria C. Sklodowska Sq.2, 20-031 Lublin, Poland (hubicki / hermes.umcs.lublin.pl)
b Fertilizer Research Institute, 24-100 Puławy, Poland

Because of increasing application of palladium in industry and its impoverishment in natural sources, ion exchange methods are of great importance for palladium recovery from used up three-way catalytic converters, chemical catalysts as well as waste waters. A wide range of commercial ion exchangers selective for Pd(II) ions is known. Gel and macroporous anion exchangers of different types should be mentioned as well.

The aim of the research was selective removal of Pd(II) from the model solutions: 0.1 ÷ 6.0 M HCl - 0.0011 M Pd(II), 0.1 ÷ 0.9 M HCl - 0.9 ÷ 0.1M HNO3 - 0.0011M Pd(II), 1.0 M ZnCl2 - 0.1 M HCl - 0.0011M Pd(II) and 1.0 M AlCl3 - 0.1 M HCl - 0.0011M Pd(II) on the weakly, intermediate and strongly basic ion exchange resins.

Therefore application of different commercial gel (Amberlite IRA-67, Duolite A-30B, Purolite A-850) and macroporous (Lewatit MP-62, Lewatit MP-64, Lewatit MP-500) anion exchangers was studied. Pd(II) sorption was carried out under dynamic and static conditions. The working ion exchange capacities, weight and bed distribution coefficients were determined from the breakthrough curves of Pd(II) ions. In order to calculate the recovery factors of Pd(II) depending on the phase contact time and aqueous phase composition, the static procedure was applied.


PC29

SYNTHESIS AND CHARACTERIZATION OF NETWORK PRECURSORS

J. WEBER, V. BOYKO, K.F. ARNDT

Institute of Physical Chemistry and Electrochemistry, Technische Universität Dresden, Mommsenstr. 4, D-01062 Dresden, Germany (karl-friedrich.arndt / chemie.tu-dresden.de)

Polymer networks with controllable morphology gain great interest during the last decade. Beside others, networks with well defined free chains are of interest. We present the synthesis and characterization of reactive graft copolymers, which can be used as precursors for polymer gels with a tuneable number of free chains of various length.

Poly(methyl vinyl ether-alt-maleic anhydride) was esterified with poly(ethylene glycol) monomethyl ether (MPEG). MPEG of molar masses of about 550, 750 and 2000 g/mol were used.

Fig. 1: General reaction scheme

Graft copolymers with various content of MPEG (up to 40 wt.-%) were successfully prepared. The remaining reactivity was proved by IR-spectroscopy. Determination of yield and branching degree was done using potentiometric titration. The average distance between branching points can be controlled in the range from 6 to 20 repeating units of maleic anhydride.

Further characterization was done with respect to the branching of the polymers. Static and dynamic light scattering, viscosity and aqueous SEC were used for a broad investigation of the solution properties.

Cross-linking of the graft copolymers is possible by two ways, leading to different network morphologies. Chemical cross-linking opens the pathway toward networks with well defined free side chains, whereas cross linking of thin films with high energy irradiation is of more interest for possible application.


PC30

SYNTHESIS, CHARACTERIZATION AND MODELING OF DOUBLE HYDROPHOBIC MODEL NETWORKS BASED ON CROSSLINKED STARS

T.K. GEORGIOUa, C.S. PATRICKIOSa

aDepartment of Chemistry, University of Cyprus, P.O.Box 20537, 1678, Nicosia, Cyprus (chpgtg1 / ucy.ac.cy)

Seven model networks of a new structure, that of cross-linked "in-out" star polymers, were synthesized by the group transfer polymerization (GTP) of the hydrophobic monomers methyl methacrylate (MMA) and n-butyl methacrylate (BuMA) and the cross-linker ethylene glycol dimethacrylate in a one-pot preparation. From the seven networks, two were the homopolymer networks of MMA and BuMA, while the remaining five were based on equimolar MMA-BuMA copolymer stars of different architectures: heteroarm (two), star block (two), and statistical. The synthesis of the networks involved at least four steps, starting from the synthesis of the linear polymers, proceeding to the preparation of the "arm-first" and "in-out" star polymers, and being completed with the cross-linking of the stars into a network. All the precursors to the networks were characterized in terms of their molecular weights using gel permeation chromatography. The sol fraction extracted from the networks was found to be equal to or lower than 20%. The degrees of swelling (DSs) in n-hexane / tetrahydrofuran (THF) mixtures of all networks increased with the solvent content in THF, a non-selective solvent, and this trend was confirmed by thermodynamic calculations. The DS in a 50-50 n-hexane-THF mixture of the statistical network was found to be the same as those of the segmented networks, suggesting absence of microphase separation in the latter type of networks, a trend confirmed by thermodynamic predictions.


PC31

SYNTHESIS AND CHARACTERIZATION OF STAR POLYMERS AND POLYMER NETWORKS CONTAINING A LABILE DIMETHACRYLATE CROSSLINKER

E. THEMISTOU, C.S. PATRICKIOS

Department of Chemistry, University of Cyprus, P.O. Box. 20537, Nicosia 1678, Cyprus (fthemistou / ucy.ac.cy, http://www.ucy.ac.cy/~chemweb/)

Anacid-labile acetal-based dimethacrylate cross-linker, di(methacryloyloxy-1-ethoxy)methane (DMΟEM) was synthesized by the reaction of 2-hydroxyethyl methacrylate (HEMA) and paraformaldehyde. Group transfer polymerization was employed to use this cross-linker in the preparation of nine hydrolyzable polymer structures: one neat cross-linker network, one randomly cross-linked network of methyl methacrylate (MMA) and seven star-shaped polymers of MMA. Gel permeation chromatography (GPC) in tetrahydrofuran (THF) confirmed the narrow molecular weight distributions of the linear polymer precursors to the stars and demonstrated the increase in molecular weight (MW) upon the addition of cross-linker for the formation of star-shaped polymers. Characterization of the star polymers in THF using static light scattering and GPC showed that the MWs and the number of arms of each star polymer increased with an increase in the molar ratio of cross-linker to initiator and with a decrease in the molar ratio of monomer to initiator. The polymers were hydrolyzed using hydrochloric acid in THF. The kinetics of hydrolysis of a star polymer was followed by GPC. Proton nuclear magnetic resonance confirmed the complete hydrolysis of the DMOEM in all the polymers characterized. The MWs of the products from the hydrolysis of the polymers synthesized were as expected.


PC32

SYNTHESIS AND CHARACTERIZATION OF CROSSLINKED POLYMER MODEL NETWORKS WITH HYDROPHOBIC SHELL AND LARGE-CORE STAR POLYMERS

D. KAFOURISa, C.S. PATRICKIOSb

aDepartment of Chemistry, University of Cyprus, P.O. Box 20537, 1678, Nicosia, Cyprus (chpgdk1 / ucy.ac.cy, http://www.ucy.ac.cy/~chemweb/)
bDepartment of Chemistry, University of Cyprus, P.O. Box 20537, 1678, Nicosia, Cyprus (costasp / ucy.ac.cy, http://www.ucy.ac.cy/~chemweb/)

A synthetic methodology for the preparation of two novel polymer structures based on methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) cross-linker was developed.� In particular, group transfer polymerization (GTP) was used to prepare shell-cross-linked polymer networks and large-core star polymers in a two-step procedure that involved the synthesis of linear MMA arms followed by their cross-linking using a mixture of MMA monomer and EGDMA cross-linker.� It was found that a high monomer / cross-linker molar ratio and a short arm length favored the formation of shell-cross-linked networks, whereas the opposite conditions favored the formation of large-core star polymers.� The number of arms of the star polymers, as determined using static light scattering, passed through a maximum as the size of their core increased, while the gravimetrically measured degrees of swelling in tetrahydrofuran of the networks increased as the cross-linker density decreased.


PC33

SHAKE GELS BASED ON LAPONITE-PEO MIXTURES: EFFECT OF POLYMER MOLECULAR WEIGHT

V. CAN, O. OKAY

Istanbul Technical University, Department of Chemistry, Maslak, 34469 Istanbul, Turkey. volkancan21 / yahoo.com , okayo / itu.edu.tr

Polymer-clay interactions in aqueous solutions receive considerable attention in recent years due to both fundamental and technological interest. These mixtures are used as rheological modifiers, as additives in coatings, and to stabilize or flocculate the colloidal dispersions. In addition, these systems exhibit interesting physical properties and, at certain concentrations, they form model reversible networks. Laponite is a synthetic disc-shaped silicate, with a thickness of approximately 1 nm and a diameter of 25 nm. In aqueous dispersions, Laponite has a strongly negative face charge and a weakly, localized positive edge charge. It was shown that, depending on the surface coverage of the Laponite particles by the polymer chains, Laponite-polymer mixtures exhibit physical properties ranging from a low viscosity liquid up to an elastic gel [1, 2]. At certain concentrations of Laponite and poly(ethylene oxide) (PEO) of molecular weight 3x105 g/mol, Laponite - PEO mixtures undergo shear-induced gelation [1]. Such gels are called as "shake gels".

In the present study, Laponite particles were bridged into a physical gel (shake gel) by PEO chains of various molecular weights between 2x105 and 9x105 g/molunder shear. The gels formed under shear transform again into a liquid if the shear stops. We investigated the effect of the molecular weight of PEO on the properties of Laponite - PEO based gels. The critical concentrations of Laponite and PEO required for gel formation as well as the moduli of elasticity of gels were determined. The results show that the molecular weight of the polymer chains significantly affects the liquid-gel boundary concentration of the mixture as well as the mechanical properties of gels. Shake gels form under certain concentrations of Laponite and PEO, corresponding to a critical surface coverage value nPEO of the Laponite particles by the polymer chains. The value of nPEO decreases as the molecular weight of PEO is increased. It was shown that strong gels with a relaxation time longer than 30 min form if the polymer molecular weight is in the range of 2x105 - 3x105 g/mol.

1) J. Zebrowski, V. Prasad, W. Zhang, L.M. Walker and D.A. Weitz, Colloids Surf. A 213, 189 (2003).

2) D.C. Pozzo and L.M. Walker, Colloids Surf. A 240, 187 (2004).


PC34

DISTRIBUTION OF DEGREES OF POLYMERIZATION IN STATISTICALLY BRANCHED POLYMERS WITH TETRAFUNCTIONAL BRANCH POINTS: MODEL CALCULATIONS

M. NETOPILÍK*, P. KRATOCHVÍL

Institute of Macromolecular Chemistry, Academy of Sciencesof the Czech Republic, 162 06 Prague 6, Czech Republic

Stockmayer's classical theory of the statistical branching of polymers [1] as modified by Thurmond and Zimm [2], and subsequently by Kilb [3], has been used to describe the evolution of the distribution of degrees of polymerization with conversion up to the gel point in a copolymerization of a vinyl monomer with a small amount of a divinyl monomer. The mass fractions of molecules with a particular number of branch points per molecule, the averages of the degree of polymerization of those molecules, and some other characteristics were calculated as functions of a complex variable-the branching parameter, g, including the composition of the monomer mixture, relative reactivities of the individual types of double bonds, and conversion. From the calculations, a few general conclusions on the behaviour of the model system can be drawn [4]. The conclusions are likely to be qualitatively valid also for systems not strictly conforming to the model.

Literature

1. Stockmayer W.H., J Chem Phys 11:45 (1943).

2. Thurmond C.D. and Zimm B.H., J Polym Sci 8:477 (1952).

3. Kilb R.W., J Polym Sci 38:403 (1959).

4. Netopilík, M. and Kratochvíl P.,Polymer International, submitted


PC35

DYNAMIC PROPERTIES OF POLYMERIC NETWORKS

F. ECKERT, V. BOYKO, K.F. ARNDT

Institute of Physical Chemistry and Electrochemistry, Technische Universität Dresden, Mommsenstr. 4, 01069 Dresden, Germany (Franziska.Eckert / chemie.tu-dresden.de)

The swelling ability of polymeric networks offers the possibility for mechanical and medical applications. Therefore the fundamental understanding of the gel dynamics is of extreme importance. Dynamic light scattering is known to be an excellent method to determine dynamic properties of gels such as network inhomogeneity and cooperative diffusion coefficients. In this work we focused on determination of cooperative diffusion coefficients (Dcoop) of poly(acrylic acid) networks in both the preparation and the fully swollen state.

Gels were prepared by free radical copolymerization in aqueous solution of acrylic acid and N,N'-methylenebisacrylamide in a broad range of monomer and cross-linker concentrations. The gels were characterized by swelling and compression tests and detailed by dynamic light scattering.

A critical monomer concentration was observed in the preparation state as well as in the fully swollen state were the ensemble averaged scattering intensity <I>E attains a maximum value. This is connected to a maximum degree of inhomogeneity. Diffusions coefficients were determined by data acquisition at different sample positions followed by heterodyne analysis of the autocorrelation functions. For gels in the preparation state a linear dependence on both monomer and cross-linker concentration was found for Dcoop. The dynamic contributions to the scattering intensity IF are a decreasing function of monomer and cross-linker concentration.

Swollen to equilibrium Dcoop increases drastically for gels with low network density whereas IF decreases. Two different concentration ranges were observed: First Dcoop decreases with increasing network fraction. After reaching a critical concentration value Dcoop increases again.

Both concentration dependencies for Dcoop in the preparation state and in the swelling equilibrium were compared with Poly(acrylic acid) solutions in the same concentration range. Correlations between networks and solutions were discussed in terms of scaling theory.


PC36

IMMOBILISATION OF GLUCOAMYLASE AND TRYPSIN ON CROSSLINKED THERMOSENSITIVE CARRIERS

A. HAMERSKA-DUDRAa, J. BRYJAKa, A. W. TROCHIMCZUKa

aFaculty of Chemistry, Wrocław University of Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland (agnieszka.hamerska / pwr.wroc.pl, jolanta.bryjak / pwr.wroc.pl, andrzej.trochimczuk / pwr.wroc.pl)

Glucoamylase and trypsin were immobilised on crosslinked thermosensitive copolymers of N-isopropylacrylamide (NIPAM) and 2-hydroxyethyl methacrylate (HEMA) or glycidyl methacrylate (GMA) using novel method of immobilisation. The method is based on the swelling properties of stimuli-sensitive polymers, which work like a pump that sucks up the enzyme on cooling and then on subsequent crosslinking of the enzyme with glutaraldehyde inside carrier, thus forming an interpenetrating network system. In such system a crosslinked carrier forms network �1�, whereas network �2� is formed by the enzyme crosslinked with glutaraldehyde.

Copolymer of NIPAM:GMA and a part of copolymer of NIPAM:HEMA were modified by aminolysis to obtain more hydrophilic carriers containing primary amino groups. Immobilisation of glucoamylase and trypsin on unmodified thermosensitive polymer and polymer hydrophilised with ethylenediamine was compared. The attention was focused on the properties of the carrier-enzyme systems particularly on the effect of crosslinking on their stability. To check the specificity of obtained preparations of glucoamylse and trypsin two kinds of high and low molecular weight substrates were used in both cases.


PC37


PC38

HYDRODYNAMIC CORRELATION LENGTHS IN SEMIFLEXIBLE POLYMER SOLUTIONS

T. UEMATSU*, C. SVANBERG, P. JACOBSSON

Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden (uematsu / fy.chalmers.se)

DNA fragments and actin filaments are essentially semi-flexible bio-polymers representing an important class in biology. As model systems for these bio-polymers, various semi-flexible polymer solutions have been extensively studied from both experimental and theoretical aspects. However, there is still no clear physical understanding of the hydrodynamics of the solutions, which in turn controls the viscoelastic properties, since the conventional physical picture for flexible polymer solutions cannot be simply applied to the systems. The shortcomings of the theory are usually ascribed to chain local stiffness strongly affecting the physical properties. However, semi-flexible polymers are not to be treated as a special class of polymers since all flexible polymers become semi-flexible when the contour lengths approach the persistence length. Even the atactic polystyrene becomes semi-flexible at short chain lengths. In the present study, we have investigated solutions of various molecular weight atactic polystyrene in a good solvent (toluene) using photon correlation spectroscopy and pulsed field gradient NMR. We have obtained the polymer concentration dependence of the hydrodynamic correlation lengths (xh), taking account of the strong increase in local solvent viscosity with increasing concentration. For high molecular weight polystyrene solutions, the concentration dependence of xh simply follows the power law behaviour previously predicted by the blob model (1). Notably, as the chain becomes shorter, xh becomes dependent of the molecular weight even above the overlap concentrations, and as xh approaches the persistence length at high concentrations a new power dependence of xh is found. The former result, the molecular weight dependence, can be a consequence of the chains becoming too short to experience three-body interchain interactions even above the so-called c** (semidilute-concentrated crossover concentration). Similarly, the latter result, the new power law behaviour, can be a consequence of interchain binary interactions dominating even above c**, where ternary interactions are dominant for high molecular weight polystyrene solutions.

(1) T. Uematsu, C. Svanberg, and Per Jacobsson, submitted to Macromolecules, and references therein.


PC39

PREPARATION OF CORE-SHELL NANOPARTICLES FROM CHITOSAN

M. BODNÁRa, J. F. HARTMANNb, J. BORBÉLYa

aDepartment of Colloid and Environmental Chemistry, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary (jborbely / delfin.unideb.hu)
bElizaNor Polymer LLC, 1 Woodmeadow Lane, NJ-08550-1323 Princeton Junction, New Jersey, USA

Chitosan is a renewable biomaterial, a functional and basic linear polysaccharide. Chitosan is prepared by N-deacetylation of chitin, resulting in a copolymer of β-[1→4]-linked 2-acetamido-2-deoxy-D-glucopyranose and 2-amino-2-deoxy-D-glucopyranose. There has been increasing interest in chitosan, because of its special set of properties, which include low or non-toxicity, biocompatibility, low immunogenicity and antibacterial properties.

We have prepared a novel biocompatible crosslinked nanoparticles based on chitosan. Natural di- or tricarboxylic acids (succinic acid, malic acid, tartaric acid, citric acid) were used for intramolecular covalently crosslinking of the chitosan linear chains. The condensation reaction of carboxylic groups and pendant amino groups of chitosan was performed by using water soluble carbodiimide. The prepared crosslinked nanosystems were stable colloid dispersion in aqueous media. These chitosan preparations can be employed as a core component of a particle with a core-shell morphology by modifying the surface of the core.

The shell was built on the core with a condensation reaction between residual free amino groups of chitosan placed on the surface of the core and functional monocarboxylic acid by using carbodiimide technique. The shell might be vinylated hydrophobic, charged or uncharged hydrophilic depending on the character of monocarboxylic acid (acrylic acid, PEG, betaine).

Core-shell nanoparticles were also prepared by self-assembly of modified chitosan linear chain. Self-assembly occurred after modification of amino groups of the chitosan linear chain using hydrophobic monocarboxylic acids and unsaturated fatty acids.

The core-shell nanoparticles might be useful for various biomedical and food applications.

This work was supported by RET (RET-06/432/2004, Grant of Regional University Knowledge Center), by ElizaNor Polymer LLC (USA) and by Universitas Alapitvany, Debrecen, Hungary.


PC40

ASSESSMENT OF SWOLLEN POLYMER MORPHOLOGY

K. JEŘÁBEK

Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, Rozvojova 135, 165 o2 Prague 6, Czech Republic; kjer / icpf.cas.cz

For a meaningful assessment of the swollen polymer morphology, there cannot be used conventional porosimetric methods (nitrogen adsorption-desorption or mercury porosimetry) requiring drying and outgasing of the investigated sample. Good morphological information on swollen polymer gels provides inverse steric exclusion chromatography (ISEC) [1-2]. The investigated material is used as filling of chromatographic column at experimental condition when the elution behavior of injected solutes with known molecular size is governed by steric effects only. By mathematical treatment of the obtained dependencies of elution volumes on the molecular size of the solutes it is possible to determine volume distribution of pores of various sizes[3,4]. Such model of the swollen polymer morphology is based on depicting of "true" pores (macro- and meso-pores) in macroreticular materials using conventional model of cylindrical pores and depicting the swollen gel as a network of randomly oriented cylindrical rods (the Ogston model). In the contribution will be discussed advantages and limitation of this approach and experiences with correlations of the obtained information with application properties of various polymer materials, mainly ion exchanger catalysts.

Halász, I.; Martin, K. Angew. Chem. Int. Ed. 17, 901 (1978).

Freeman, D. H.; Poinescu, I. C. Anal. Chem. 49, 1183 (1977).

Jeřábek, K. Anal. Chem. 57, 1592 (1985).

Jeřábek K.: Inverse steric exclusion chromatography as a tool for morphology characterization. In: Cross-Evaluation of Strategies in Size-Exclusion Chromatography, ACS Symposium Series 635, p. 211 - 224, M. Potschka, P. L. Dubin (Eds.), American Chemical Society, Washington 1996.


PC41

DYNAMIC VISCOELASTIC CHARACTERIZATION OF A REACTIVE EPOXY-AMINE SISTEM MODIFY WITH SEPIOLITE

A. NOHALES, L. SOLAR, C.M. GOMEZ

Institut de Ciència dels Materials, Departament de Química Física, University of València, Dr Moliner 50, 46100 Burjassot (Valencia), Spain (andres.nohales / uv.es)

Polymer nanocomposites have been extensively studied in the last years as an increasing demand for advanced materials with better properties to meet new requirements or to replace existing materials. Among them, thermoset nanocomposites have received little attention. In this paper we study the isothermal curing of sepiolite/epoxy nanocomposites in order to investigate the influence of the inorganic filler on the gelation and vitrification times.

Sepiolite, an hydrous magnesium silicate, was used as inorganic filler. A diglycidyl ether of bisphenol A (DGEBA) GY250 was used as epoxy resin. The curing agent was polypropylene oxide diamine (Jeffamine D230). Stoichiometric mixtures of epoxy-amine were used. Isothermal rheological experiments (65-85 C) were conducted on a TA AR-1000 rheometer using parallel plate mode in multiple waveform dynamic rheology in the range 5-50 rad/s.

The effect of the clays on the gel and vitrification times can be seen by plotting the storage (G') and loss moduli (G") as a function of time. Over the frequency range investigated, the frequency dependence of both moduli, G´ and G´´, were well described by the power laws: G´~ωn and G´´~ωm for all the systems investigated. The gelation time of all systems was taken from the crossover in tand. For comparison, the gel time was also determined from the G'/G" crossover due to rapid increase in elasticity with gelation. At these critical times, the frequency dependence of G´ and G´´ follow the same power law with the same exponent n and m. The power law was interpreted in terms of the fractal dimension of the cluster. The exponents decrease in presence of sepiolite. In all systems a decreasing in gelation and vitrification times were found in presence of sepiolite.

Acknowledgements: Financial support from projects MAT2002-03485 and GV04B133 is gratefully acknowledged.


PC42

FORMATION AND PROPERTIES of poly(N,N-dimethylacryl amide) hydrogels

N. ORAKDOGEN, O. OKAY

Istanbul Technical University, Department of Chemistry, 34469 Maslak, Istanbul, Turkey, Fax: +90-212-2856386 okayo / itu.edu.tr, norakdogen / srv.ins.itu.edu.tr

The equilibrium swelling degree in various solvents, the modulus of elasticity, and the spatial inhomogeneity of poly(N,N-dimethylacrylamide) (PDMA) hydrogels were investigated.� The selection of N,N-dimethylacrylamide (DMA) as a monomer is due to the fact that it is a liquid at room temperature and fully miscible with water.� Thus, PDMA hydrogels could be prepared in aqueous solutions at monomer concentrations from a few percent up to 100 % (without the use of a solvent).� In this way, we were able to investigate the hydrogel properties over the whole range of the polymer concentration.� The hydrogels were prepared by free-radical crosslinking copolymerization of DMA and N,N�-methylenebis(acrylamide) (BAAm) at a fixed crosslinker ratio but at various initial monomer concentration.� The degree of dilution of the networks after their preparation was denoted by , the volume fraction of crosslinked polymer after the gel preparation.

Both the linear swelling ratio of gels D/D0 and the polymer volume fraction in the equilibrium swollen gel n2,eq were found to increase with increasing� .�� Depending on the value of , three different gel regimes were observed: (1) For �< 0.3, increasing �decreases the extent of cyclization during crosslinking so that the effective crosslink density of gels increases with rising . (2) For 0.3 < �< 0.7, increasing �reduces the accessibility of the pendant vinyl groups during crosslinking due to the steric hindrance at high polymer concentrations. As a result, the effective crosslink density of gels decreases with increasing . (3) For �> 0.7, the modulus of elasticity increases sharply with increasing �due to the increasing extent of chain entanglements.

PDMA hydrogels subjected to swelling measurements in several solvent mixtures showed that the hydrogels exhibit reentrant phase transitions in acetone/water, THF/water, as well as in dioxane/water mixtures.�

Measurements of the degree of spatial gel inhomogeneity in PDMA gels showed that these gels are much more homogeneous than the poly(acrylamide) (PAAm) hydrogels formed under the same conditions.� The results were explained in terms of the relative positions of the critical overlap concentration c* and the polymer concentration at the onset of gelation in both gelling systems.


PC43

EFFECT OF SWELLING ON SPATIAL INHOMOGENEITY IN POLY(ACRYLAMIDE) GELS FORMED AT VARIOUS MONOMER CONCENTRATIONS

M.Y. KIZILAY, O. OKAY

Istanbul Technical University, Department of Chemistry, 34449 Maslak, Istanbul, Turkey Fax: +90-212-2856386 kizilaym / itu.edu.tr / okayo / itu.edu.tr

In the present work the effect of swelling on the spatial inhomogeneity in poly(acrylamide) (PAAm) gels has been investigated with the static light scattering measurements. Four sets of gels were prepared using N,N'-methylenebis(acrylamide) (BAAm) as a crosslinker at a fixed crosslinker ratio X but at various initial monomer concentrations. The crosslinker ratio X (the mol ratio of BAAm to the monomer acrylamide) was fixed at 1/50, 1/61.5, 1/66,and 1/100 in each set of gels.

The gels, both at the state of preparation and at the equilibrium swollen state in water, exhibit a maximum degree of spatial gel inhomogeneity at a critical monomer concentration (). shifts toward smaller concentrations as X is decreased or, as the gel swells beyond its swelling degree after preparation.(Figure1) Swelling enhances the extent of spatial inhomogeneity in PAAm gels and, this enhancement mainly occurs at low crosslinker ratios. It was also shown that three different effects, namely crosslinker, concentration, and swelling effects determine the extent of inhomogeneities in gels formed at various monomer concentrations. The theoretical prediction of the Panyukov - Rabin theory was found to be in qualitative agreement with the experimental findings.

Figure 1 : Excess scattering intensities Rex,q at q = 1x10-3 Ao -1 shown as a function of . The filled and open symbols represent data of gels at the state of their preparation and at the equilibrium swollen state in water, respectively.


PC44

Effect of preparation temperature on the properties of 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS) based gels

M.M. OZMEN, O.OKAY

Istanbul Technical University, Department of Chemistry, 34469, Istanbul, Turkey (ozmenmurat / yahoo.com, okayo / itu.edu.tr)

In this study, a series of gels based on the monomer 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS) and the crosslinker N,N'-methylenebisacrylamide (BAAm) was prepared by free radical crosslinking copolymerization in aqueous solutions. The gel preparation temperature was varied between +250 C and -220 C. The gels prepared at temperatures below and above the bulk freezing temperature of the polymerization system are called as cryogels and hydrogels respectively. The swelling/deswelling kinetics, the morphologies as well as the elastic properties of the gels formed at various temperatures were studied.

The results show that the elastic modulus of gels rapidly increases while their swelling capacity rapidly decreases as the gel preparation temperature decreases below -7.50C. Scanning electron microscopy studies revealed that the gels formed below -7.50C consist of a discontinuous morphology with polyhedral pores of sizes 30 - 50 mm in diameter, while those formed at or above -7.50C exhibited a continuous morphology (Figure 1). Addition of sodium chloride in the gel formation system further decreased the size of the pores down to about 10 mm. Cryogels obtained at temperatures below -100C exhibited super fast responsive properties against the external stimuli.

(A) (B)

FIGURE 1: The morphology of AMPS gels prepared at -7.50C (A) and -140C(B). Magnification = 300 x.


PC45

Organic-Inorganic Hybrid Star-Like Copolymers

J. VRAŠTILa, V. ŠPAČEKa, L. MATĚJKAb, B. RÝZNAROVÁc

aSynpo, S. K. Neumanna 1316, CZ-532 07 Pardubice, Czech Republic (synpo / synpo.cz)
bInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic (office / imc.cas.cz)
cInstitute of Polymeric Materials, University Pardubice, Čs. Legií nám. 565, CZ-532 10 Pardubice, Czech Republic (upm.fcht / upce.cz)

This work is focused on preparation of hybrid star polymers as potential precursors for nanoparticles. The idea of the preparation such type of polymer systems containing functional trimethoxysilyl groups comes from the enormous increase of interest in nanocomposites. These structured star polymers are supposed to serve as a reinforcing agent.

The group transfer polymerization of methacrylates was used for preparation of star polymers with controlled structure. An appropriate approach to the preparation of organic-inorganic hybrids, with in situ formed inorganic phase, is the hydrolytic sol-gel process. In the case of the star polymers, the sol-gel process was rather utilized for cross-linking. Compact domains were formed. These domains could significantly modify properties of polymer binders.

Five types of methacrylic star polymers were synthesized by the "arm-first" method star polymer formation by the addition of tetrafunctional monomer to living linear poly(methyl methacrylate). 3-trimethoxysilylpropyl methacrylate, 2-dimethylaminoethyl methacrylate, and isobutyl methacrylate were used for the arm synthesis. Ethylene glycol dimethacrylate serve as a tetrafunctional monomer in the core-forming stage. These star molecules were cross-linked by the sol-gel process in the next step.

The star polymers were characterized by SEC-MALS. Miscibility with water and the gel point were determined. The hardness development of prepared film was observed during the sol-gel process. The cross-linked reaction caused the formation of hard brittle polymer films.


PC46

Viscoelastic properties of re-extruded potato starch

R. ZIOBRO, P. PTASZEK*, A. PTASZEK

University of Agriculture, Faculty of Food Technology, 30-149 Krakow, ul. Balicka 122, (*ptaszekp / op.pl).

Extrusion is a method of physical modification of starch, commonly used in food technology. Extruded starch is an amorphous mixture of branched and linear glucan and its physical behaviour differs from native starch, which is organised in granules and contains crystalline regions. Reextrusion of starch changes molecular properties of starch glucans, but no studies were performed on its viscoelastic properties after solubilisation in water or other solvents, such as DMSO. The aim of the study was to check the influence of reextrusion on viscoelastic behaviour of systems containing processed potato starch.

The results demonstrate that the molecular degradation of starch glucans results in changes in viscoelastic properties of their solutions in water and DMSO. The sample obtained after first extrusion was soluble in water, and gave 10% pastes behaving as fluid (G" larger than G'). The dependence of storage and loss moduli of reextruded samples indicated the formation of 3-dimensional network.

Solubilisation in DMSO of extruded and reextruded starch (10%) resulted in the formation of gel. The temperature dependence of G revealed slight increase of melting temperature of the system after reextrusion.

Fig. 1 Temperature dependance of loss and storage moduli of extruded and reextruded starch dissolved in DMSO

This work is supported by the Polish Scientific Committee grant no. 2 P06T 013 28


PC47

POROUS POLYACRYLAMIDE MONOLITHS AS STATIONARY PHASES FOR HYDROPHILIC INTERACTION ELECTROCHROMATOGRAPHY.

V. GURYČA1,2,3, J. MICHÁLEK2, V. PACÁKOVÁ1, M.V. NOVOTNÝ3, J. ŠIRC1,2

Department of Anal. Chemistry, Faculty of Sciences, Charles University, Prague
Institute of Macromolecular Chemistry, Academy of Sciences, Prague
Department of Chemistry, Indiana University Bloomington, USA

Porous polymer networks (e.g. monoliths) are gathering great significance by serving as stationary phases for numerous analytical applications. Their preparation usually proceeds in situ in a porogenic media harbouring a mixture of good and poor solvent in regards of growing polymer chains. This technique of polymerization provokes phase separation and syneresis effects leading to a creation of opaque, macroporous structures [1] allowing facile flow of mobile phase during separations.

For the enormous efforts of analytical glycobiology to reveal the structure of glycan residues cleaved from cellular glycoproteins, the capillary electrochromatography (CEC) of oligosaccharides in porous acrylamide media has been employed [2]. The polymerization feed consists of a copolymerization pair acrylamide + N,N'-methylenebisacrylamide (these compounds form a rigid polymer backbone) and functional hydrophilic ligands such as N-[Tris(hydroxymethyl)methyl]acrylamide and ionic vinylsulfonic acid.

From chromatographical point of view it is possible to alter separation capacity of various compounds by copolymerization of suitable separation ligands [3]; interestingly the "pure" acrylamide matrix was capable to fairly resolve branched glycan forms in hydrophilic interaction mode even without any other polar ligand embodied. Furthermore; the "pure" acrylamide network formed with more rigid crosslinker warrants the maximum efficiency of separations (routinely up to 350 000 plates per meter for tagged oligosaccharides), resolution of the branched glycan isomers and the highest permeabilities of columns.

The structure of continuous rod was investigated with porosimetry, electron microscopy and swelling methods. Evidently, in the dry state there are voids present in the monolith only in mesoporous range which is not passable for chromatography purposes [4]. Thus the macroporosity in the network must be set up within a reswelling process in various solvents (mobile phases) [5]. This factor steers the great potential of the innovated polymer rod predominantly to the electrokinetically driven separation methods.

We are indebted to National Institute of Health - USA; Indiana Genomic Initiative, Indiana University - USA; Josef Hlávka Foundation - Czech Rep.; Fund Mobility, Charles University - Czech Rep.; and Academy of Sciences of the Czech Rep., project AVOZ40500505 for financial support.

[1] Okay, O., Prog. Polym. Sci. 2000, 25 , 711-779.

[2] Que, A. H. and Novotny, M. V., Anal. Bioanal. Chem. 2003, 375 , 599-608.

[3] Palm, A. and Novotny, M. V., Anal. Chem. 1997, 69 , 4499-4507.

[4] Hjerten, S., Vegvari, A., Srichaiyo, T., Zhang, H. X., Ericson, C., and Eaker, D., J. Cap. Electroph 1998, 5 , 13-26.

[5] Beranova, H. and Dusek, K., Collect. Czech. Chem. Commun. 1969, 34 , 2932-2941.


PC48

DLS STUDY OF EYE LENS PROTEINS DISPERSIONS: THE EFFECT OF TEMPERATURE

A. GIANNOPOULOUa,b, A. J. ALETRASc, N. PHARMAKAKISd, G.N. PAPATHEODOROUa,e, S. N. YANNOPOULOSa

aFORTH-ICE/HT, P.O Box 1414, GR-26504, Patras, Greece, sny / iceht.forth.gr
bDepartment of Pharmacy,University of Patras, GR-26504, Patras, Greece, athina / iceht.forth.gr
cDepartment of Chemistry, University of Patras, GR-26504, Patras, Greece
dSchool of Medicine, University of Patras, GR-26504, Patras, Greece
eDepartment of Chemical Engineering, University of Patras, GR-26504, Patras, Greece, gpap / iceht.forth.gr

Dynamic light scattering (DLS) is a powerful technique for the non-invasive and early diagnosis of eye diseases, i.e. cataract. Age-related cataract is caused in the nuclear region of the lens by the gradual aggregation of its proteins (crystallins) upon ageing.

The nucleus of the lens, being a very dense dispersion of crystallins ca. 400 mg/ml, exhibits a very complicated pattern of dynamics, at least four relaxational modes. To find possible indicators of the cataract onset one has first to understand the origin of each mode. Therefore, a concentration dependence study of the crystalline dynamics has to be undertaken. In this work, lens extracts from bovine eyes were first homogenized, then centrifuged for 1 h at 20000 g after dilution in a physiological buffer (phosphate buffer: ionic strength 150 mM, pH 7.3) and finally were highly concentrated. Dispersions at various concentrations were subjected to temperature variations in the range 37-2 oC. The results indicate that new relaxational modes at long time scales appear with a progressive increase of protein concentration. These modes are presumably associated with modifications in the aggregation state of the crystallins.

In the present study the effect of decreasing temperature on the dynamical behavior of lens proteins will be presented for two extreme concentrations (300 and 50 mg/ml). Two modes are evident at the low-concentration solution which correspond to two different "particle" sizes, i.e. 17 and 120 nm. Both sizes seem to be unaffected by decreasing the temperature.

At 300 mg/ml the appearance of three relaxational modes is obvious in the range 37-20 oC. Below 20 oC a new mode appears at a longer time scale that reflects aggregation of the particles. Its implication to the cataract onset will be discussed.


PC49

SWELLING KINETICS OF POLY(ACRYLIC ACID) HYDROGEL IN DISTILLED WATER

J. JOVANOVICa, B. ADNADJEVICb, D. USKOKOVICa

aInstitute of Technical Sciences of the Serbian Academy of Science and Arts, Knez Mihailova 35, 11000 Beograd, Serbia and Montenegro
bFaculty of Physical Chemistry, Studentski trg 16, 11000 Beograd, Serbia and Montenegro

Due to characteristic properties such as swellability in water, hydrophilicity, biocompatibility, and lack of toxicity, hydrogels have been utilized in a wide range of biological, medical, pharmaceutical and environmental applications. [1,2]. The application of hydrogels could be significantly affected by their swelling properties. Although many works concerns hydrogels swelling kinetics, mostly of them swelling kinetics of hydrogels formally described as first or second reaction order, or as process controlled by diffusion.

In this work, a hydrogel of crosslinked poly(acrylic acid) with well-defined structural properties was synthesized and well characterized. The swelling kinetics of the synthesized hydrogel at temperatures from 25o to 45oC was investigated in distilled water.It was shown that swelling process of this hydrogel couldn't described by the so-called Fickian diffusion process. Namely, this process in specific parts of the swelling could be described as first order (up to maximum 0.9% of SDeq) and as second order kinetics (for swelling degrees higher than 0.8% of SDeq). A swelling mechanism for PAA hydrogel swelling in distilled water was suggested to be described as topochemical reaction. Based on this model swelling kinetics curves are obtained. It was demonstrated that at all applied swelling temperatures swelling process entirely can be described by this model. The swelling kinetic parameters: activation energy (Ea) and pre-exponential factor (A), were determined.

[1] N.A. Peppas, A.G.Mikos, "Hydrogels in Medicine and Pharmacy", Vol. I: Fundamentals, CRC Press, Boca Raton, Florida 1986. p. 2-23;

[2] B.D. Ratner, A.S. Hoffman, in "Hydrogels for Medical and Related Applications", Andrade and Andrade, eds., American Chemical Society, Washington, DC, 1976, p.1-36;