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Interactions of Crosslinked Copolymers with Organic Compounds Studied by Inverse Gas Chromatography
J. Hradil
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského sq. 2, CZ-162 06 Prague 6, Czech Republic
e-mail: hradil@imc.cas.cz
Inverse gas chromatography was used to study phase transition in polymers and the interaction of organic compounds with macroporous and hypercrosslinked copolymers, which find application as sorption and separation media. Polarity, phase transitions and interaction parameters of crosslinked copolymers with some molecular probes were estimated from specific retention volumes. Contributions of disperse and polar interactions were separated. Hence, Gibbs adsorption energy, ΔGa, is given as a contribution of dispersion, orientation, and induction forces and H-bonds, ΔGH,
ΔGa = αs [αl 3 Is Il/2(Is + Il) + μl2] + μs2(2μl2/3kT + αl) + ΔGH
where α is effective polarizability, I ionization potential, and μ dipole moment; subsripts s and l stand for the sorbent and the solute, respectively.
For polarity relations of various adsorbents and stationary phases, the chromatographic polarity scale developed by Rohrschneider and Kováts is used. The following row of increasing polarity of polymeric adsorbents has been obtained:
Chromosorb 106 < Chromosorb 107 < MMA-EDMA < Porapak T <
MMA-HEMA-EDMA < Chromosorb 104 < bead cellulose < HEMA-AN-EDMA
Information about the phase transition in the polymer can be obtained from the retention diagram - the function of ln Vg vs. 1/T - of molecular probes. For macroporous divinylbenzene and methacrylate copolymers, deviations from linearity were observed in the region of Tg. Deviations from linearity in the retention diagram are explained by changes in the segmental mobility on the internal surface of the copolymer. In hypercrosslinked copolymers, deviations from linearity in the retention diagram were not observed. The absorption mechanism is in agreement quasi-elastic behaviour of hypercrosslinked copolymers. It is assumed that the retention mechanism in porous polymers is rather complex.
This study was supported by Institute of Macromolecular Chemistry AS CR (Project No. 5312) and by the Academy of Sciences of the Czech Republic (Project No. AVOZ4050913), which author gratefully acknowledge.
RATIONALIZING THE MEANING OF COEFFICIENTS IN FLORY - HUGGINS APPROACH TO PoLYMER - SOLVENT INTERACTIONS
E. Lucchelli, L. Caccianotti
Centro Ricerche Novara "Istituto Guido Donegani", Polimeri Europa, Via Giacomo Fauser 4, I - 28100, Novara, Italy
E-mail: ernilio.lucchelli@polimerieuropa.com
Flory - Huggins interaction pararneter for a polymer solution can be represented as the product of two functions, which separately take into account the effects of the volume fraction of polymer and of temperature. The latter factor contains three constants, usually viewed as best - fit coefficients.They were expressed in terms of two thermodynamic quantities, namely, the excess partial molar heat capacity of the solution and a reference temperature, thus giving them a physical meaning. The formulae so obtained were tested with satisfactory results in the cases of two solutions of polystyrene in acetone, as well as for two polymer blends (PC/PMMA and PS/PVME.) Furthermore, an attempt was made to calculate the above mentioned reference temperature from data referring to the phases in solution.
MONOLAYERS AND SELF-ORGANIZED DISCRETE MULTILAYERS OF MESOPHASE POLYORGANOSILOXANES, FORMED ON SUBPHASES OF WATER, POLYOLS AND THEIR SOLUTIONS.
S.I.Belousov, D.I. Korochkin, Y.K.Godovsky.
Karpov Institute of Physical Chemistry, Ul.Vorontzovo Pole 10, Moscow 103064, Russia, belousov@cc.nifhi.ac.ru
It has been established that many of the novel cyclolinear polysiloxanes (CLPOS) form either columnar or quasi-2d-nematic mesophases in the bulk state in spite of their flexible nature. Moreover, as a result of this mesophase behaviour CLPOS's are capable building ordered Langmuir monolayers. The most striking feature of the mesophase LM of CLPOS, however, happened to be their self-organized collapse, resulting in the formation of stable multilayers during the lateral compression. Several plates occur at ratios of the area that are consistent with stepwise layer growth from monolayer to bilayer, bilayer to trilayer, etc., continuing up to seven-ten layers. For our knowledge, this is the maximal number of LM self-organized in polymeric multilayers directly on the liquid/air interface during the continuos lateral compression. For more than ten samples a linear dependence of the pressure jump value of steps versus isotropization temperature has been found. The effects of subphases, chemical structure, side substituents, molecular weight, temperature, various rate regimes of film deformation, and chain flexibility on the pattern of surface pressure isotherms was studied. A model has been suggested in which the steps are treated as a result of sliding macromolecules organized in columnar mesophase from layer to layer without breaking hexagonal order.
The floating films were studied with, Langmuir trough, Brewster Angle Microscopy (BAM), Scanning Force Microscopy (SFM), X-ray reflectivity, Grazing-Incidence X-Ray Diffraction (GIXD), X-Ray Standing Wave (XRSW) at Total Reflection (TR), surface rheology and molecular modeling.
Summing up, we can conclude that mesomorphic CLPOS are a unique class of polymers, which are very perspective for the development of methods of creating of the nanoscale ordered ultrathin films directly on liquid surfaces.
The work is carried out at financial support of funds: INTAS 97-0485, RFBR (grants 01-03-32173; 02-03-06581).
EFFECT OF THE SOLVENT SYSTEM IN DISPERSION POLYMERIZATION ON PROPERTIES OF METHACRYLATE–BASED MAGNETIC MICROSPHERES
aN. SEMENYUK, bD. HORÁK
aLviv Polytechnic National University, S. Bandera St. 12, 79013 Lviv, Ukraine
bInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovský Sq. 2, 162 06 Prague 6, Czech Republic
Recent developments in the dispersion (co)polymerization of polar monomers, such as 2-hydroxyethyl (HEMA) and glycidyl methacrylate (GMA) in the presence of a ferromagnetic fluid are discussed including particle formation in an aqueous alcoholic and mixed-solvent system composed of toluene/2-methylpropan-1-ol. Magnetic colloids (ferrofluids) were produced by co-precipitation of Fe(II) and Fe(III) salts in an alcoholic solution and stabilized with several kinds of coating. Influence of parameters of dispersion polymerization, in particular medium solvency, on the particle size and distribution of both nonmagnetic and magnetic hydrophilic microspheres was investigated. Polarity of the polymerization medium was characterized in terms of its solubility parameter value. The solvent power (the difference in solubility parameters between the polymer and solvents) determined the critical molecular weight above which the polymer precipitates and, ultimately, the particle size. In agreement with the general observation that any change in the system enhancing the solubility of the polymer formed increases the particle size, solubility of oligomers increases with decreasing solvent power of the reaction medium for the growing polymer chain, fewer nuclei precipitate at the beginning of the polymerization, and, correspondingly, larger particles are formed. The conditions and a finite solvency window in which it was possible to prepare monodisperse magnetic microspheres were determined. Controlling the reaction medium polarity by changing composition of a mixed solvent made thus possible to control the particle size and distribution. Moreover, the particle size and their distribution depend on the relative amounts of ferrofluid, monomers and the HEMA/GMA ratio. The magnetic microspheres can be used as carriers of biologically active compounds. Compared to nonmagnetic particles, their advantages include easy separability, low mechanical stress during operation, possibility of purification on a small scale, repeated usage and amenability to automation.
This work was supported by the Grant Agency of the Czech Republic No. 525/02/0287 and by the Academy of Sciences, project No. AVOZ4050913.
Interaction between Charged Cellulose Matrix and solutions of cationic surfactants
N.E. KOTELNIKOVA, E.F. PANARIN
Laboratory of Physical Chemistry of Polymers, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoy pr. 31, St. Petersburg 199004, Russia; e-mail: kotel@mail.rcom.ru
Interactions between charged insoluble cellulose matrix and solutions of low molecular weight cationic surfactant (N-dimethylbenzylalkylammonium chloride - DMBAAC) and its polymeric analogue (complex of DMBAAC and copolymer of N-vinylpyrrolidone with crotonic acid) have been studied by adsorption kinetics as well as by WAXS, IR, and XPS spectroscopy and raster electron microscopy. It was found that DMBAAC is strongly bound to cellulose. When concentration of DMBAAC solutions is lower than critical concentration of micellation, this binding proceeds step-by-step via electrovalent interaction of ammonium groups of DMBAAC molecules with carboxyl groups on cellulose surface, leads to two-layers adsorption, and causes matrix swelling and partial decomposition. When concentration of DMBAAC solutions is higher than critical concentration of micellation, its micelles are bound to cellulose via anchor mechanism. DMBAAC is responsible for interaction between cellulose and polymer analogue of DMBAAC. Due to antimicrobial activity of applied surfactants, adsorption complexes cellulose-surfactants are prospective for biomedical application.
1H NMR RELAXATION STUDY OF POLYMER-SOLVENT INTERACTIONS DURING THE THERMOTROPIC PHASE TRANSITION IN AQUEOUS SOLUTIONS
J. SPĚVÁČEKa,b, L. HANYKOVÁb
aInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic
bCharles University, Faculty of Mathematics and Physics, V Holešovičkách 2,
180 00 Prague 8, Czech Republic
It is well known that some polymers, including poly(vinyl methyl ether) (PVME), in aqueous solution exhibit a lower critical solution temperature (LCST), i.e., they are soluble at low temperatures but heating above the LCST results in phase separation1. On molecular level, such phase separation is assumed to be macroscopic manifestation of a coil-globule transition. In this work we studied the structural changes and polymer-solvent interactions during the thermotropic phase transition in PVME/D2O solutions in a broad range of polymer concentrations (0.1-60 wt.-%), combining the measurements of 1H NMR spectra, spin-spin (T2) and spin-lattice (T1) relaxation times.
At temperatures above 308 K, a marked broadening was observed for a major part of PVME units in 1H NMR spectra. At the same time, a very short component (T2 = 0.85 ms (CHOCH3) and T2 = 0.30-0.72 ms (CH2)) dominates the spin-spin relaxation of PVME protons. For CH2 protons this component increases with increasing concentration of the solution, showing that globular-like structures are more compact in dilute solution in comparison to semidilute or concentrated solutions, where globules probably contain a certain amount of water. This is in accord with measurements of nonselective and selective T1 relaxation times of HDO molecules which evidenced that for semidilute and concentrated solutions above 308 K, a part of HDO molecules is bound to (in) PVME globular structures. Such HDO exhibits a slow-motion behavior (w 0t c>1), with fast exchange between bound and free sites with regard to T1 values (~20 s).
Acknowledgment: This work was supported by the Academy of Sciences of the Czech Republic (project No. K4050111) and the grant Agency of the Charles University (grant No. 164/20B)
References:
1. L. Hanyková, J. Spěváček, M. Ilavský: Polymer 42, 8607 (2001)
1H NMR STUDY OF PHASE TRANSITION OF UNCHARGED AND NEGATIVELY CHARGED POLY(N-ISOPROPYLMETHACRYLAMIDE) IN D2O SOLUTIONS
L. STAROVOYTOVAa, J. SPĚVÁČEKa,b, L. HANYKOVÁa, M. ILAVSKÝa,b
aCharles University, Faculty of Mathematics and Physics, V Holešovičkách 2,
CZ-180 00 Prague 8, Czech Republic
bInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského Sq. 2, CZ-162 06 Prague 6, Czech Republic
Heating of aqueous poly(N-isopropylmethacrylamide) (PIPMAAm) solutions above the lower critical solution temperature (LCST) results in phase separation due to changed balance between various polar and non-polar interactions. In this study we used 1H NMR spectroscopy to investigate the structural and dynamic changes during the phase transition of uncharged PIPMAAm and negatively charged copolymers of IPMAAm and sodium methacrylate (1-10 mol%) in D2O solutions at polymer concentrations c = 0.1 – 10 wt.-%.
Above the LCST transition, a reduction in the absolute integrated intensities was observed for PIPMAAm lines in high-resolution NMR spectra, due to a pronounced decrease in the PIPMAAm mobility. The phase transition of all uncharged samples was found in the temperature range 314 – 320 K; the fraction pmax of the phase-separated units above the transition region was ~ 1 independently of polymer concentration. Introducing the charges on the polymer chains led to the dependence of the transition region on degree of ionization and polymer concentration. For the solutions with highest concentration c = 10 wt.-%, a shift of transition to higher temperatures was observed with increasing degree of ionization (due to increasing hydrophilic character of charged PIPMAAm chains). At the same time, transition region has become broader and the fraction pmax decreased with increasing ionization. On the contrary, the ionic solutions with c = 0.1 wt.-% have shown virtually a jump transition and the increasing degree of ionization shifted the transition temperature to lower values; pmax values were equal to 1 for all degrees of ionization.
Acknowledgment: This work was supported by the Grant Agency of the Charles University (grant No. 164/2001B), Grant Agency of the Academy of Sciences of the Czech Republic (project No. IAA4050209) and Ministry of Education, Youth and Sports of the Czech Republic (project MSM 113200001).
GELATION AND IN SITU FIBRILLATION OF FLEXIBLE-CHAIN POLYMERS DURING SYNTHESIS OF POLY(VINYL ALCOHOL) AND POLYACRYLONITRILE
W.S. Lyooa, S.O. Sonb, B.C. Jib, C.J. Leec
aSchool of Textiles, Yeungnam University, Kyongsan 712-749, Korea, wslyoo@yu.ac.kr
bDepartment of Dyeing and Finishing, Kyungpook National University, Taegu 702-701, Korea
cElectronic Materials and Devices Research Center, Korea Institute of Science and Technology, Seoul 130-650, Korea
In this study, two examples of gelation and in situ fibrillation were presented. Firstly, the syndiotacticity-rich (syndiotactic diad content of 57-65%) high molecular weight (number-average degree of polymerization of 4500-20000) poly(vinyl alcohol) (PVA) microfibrils were directly produced via the saponification reaction of poly(vinyl pivalate) (PVPi) by controlling structural factors such as molecular weight and stereoregularity of PVA chains, and appetence between PVA and solvent without existing spinning procedures. By examining and observing the changes of flow birefringence, shear viscosity of reaction solution, degree of saponification, and shape of reaction product during the saponification reaction, the following novel formation mechanism of high strength microfibrillar PVA fiber is proposed. As PVPi converts into syndiotactic PVA by means of saponification using saponifying agents containing water, an oriented gel structure appears first by the interaction between water and hydroxyl groups of syndiotactic PVA formed during the saponification reaction, and then the microfibrillar structure is formed by the collapse of water-PVA interbridges and the resultant chain packing between syndiotactic PVA molecules. The larger the syndiotacticities of both PVPi and PVA, the higher the molecular orientation and the smaller the hydroxyl groups in P(VPi-VA) copolymer needed for in situ fibrillation. The well oriented microfibrillar PVA fiber prepared by such a manner had irregular cross-sections, needle-point-like ends, accumulated ultrafine microfibril structure. Secondly, polyacrylonitrile (PAN) microfibrils were prepared directly via the solution polymerization of acrylonitrile at specified ratios of controlling solvent dimethyl sulfoxide (DMSO) to non-solvent tert-butyl alcohol. At first, gel formation occurred due to the interaction between DMSO and the cyano groups of PAN. The microfibrillar structure was then formed through the phase separation of PAN molecules from the gel. It is shown that very small variations in the solvent/non-solvent ratio facilitate a major change in the gelation and phase separation processes.
POTENTIAL BIOMEDICAL APPLICATIONS OF MAGNETIC PVA HYDROGELS
C.MIJANGOS, A.SARAFIAN, R.HERNANDEZ, D.LOPEZ
Instituto de Ciencia y Tecnología de Polímeros, Consejo Superior de Investigaciones Científicas, calle Juan de la Cierva 3, 28006 Madrid, Spain
Aqueous solutions of atactic poly(vinyl alcohol) produce physical gels when submitted to a series of freezing-thawing cycles. The freezing-thawing cycles produce interstitial domains of high polymer concentrations due to water crystallization. The crystallization of the polymer chains belonging to these highly-concentrated domains leads to the gelation of the system.
Magnetic field-sensitive gels, called ferrogeles, can be prepared from PVA solutions in ferrofluids following the same procedure as for PVA cryogels in water. A ferrofluid or a magnetic fluid is a colloidal dispersion of monodomain magnetic particles with a typical size of about 10 nm.
Ferrogels are soft smart materials whose elastic and thermodynamic properties are a strong function of the field strength imposed upon them. In uniform magnetic fields, a ferrogel experience no net force. When it is placed into a spatially nonuniform magnetic field, forces act on the magnetic particles producing shape changes in the gel. The shape change, accompanied with changes in the swelling equilibrium, can be bending, elongation, contraction, and a combination of these basic distortions.
The coupling of elasticity, degree of swelling, retention capacity, etc., with external magnetic fields in gels allows to study the potential applications of magnetic gels in the development of switches, sensors, micromachines, biomimetic energy-transducing devices, and controlled delivery systems.
In this communication we report on both material preparation and characterization of a poly(vinyl alcohol) magnetic hydrogel and the study of the potential application of this system as a medium for the controlled release of drugs.
DIELECTRIC RELAXATION OF XEROGELS BASED ON POLY(ACRYLAMIDE) AND POLY(VINYL ALCOHOL)
N. MELNIK, A. ALEXEYEV, L. MOMOT, N. KUTSEVOL,
V. SYROMYATNIKOV
Kiev Taras Shevchenko National University, Faculty of Chemistry, 60 Vladimirskaya str., 01033, Kiev, Ukraine. E-mail: innusya1981@ramber.ru
Recently the series of water-soluble polymers are utilized in modern technologies, as polymeric networks with a low volumetric share of polymer and the properties of such networks are determined, first of all, by the composite structure of polymeric system. As the method of a dielectric relaxation is very sensitive to the most inappreciable changes in the polymer structure, we have tried to apply it for an estimation of the structural peculiarities of the polymeric networks obtained on the basis of water-soluble graft copolymers with interacting components.
The comparative examinations of dielectric properties of the polymeric networks obtained on the basis of dried gels with a small water content - xerogels of individual components of graft copolymer - poly(vinyl alcohol) (PVA) and poly(acrylamide) (PAA), and also graft copolymer PVA-PAA in an interval of frequencies 400 Hz- 50 kHz and temperatures 80-450 К are carried out.
For PVA two types of relaxation processes were determined, the first one, low-temperature, was a process of b - relaxation, caused by the microdeformation of a chain due to the dipoles’ mobility of polar hydroxyl groups, and the second one corresponds to the a -relaxation process and is connected with segmental shifts of molecular dipoles, which were found in the vitreous state. For the first time for PVA structural - phase transition on a background b - relaxation of its weakly polar amide groups, which temperature position depends on the density of the hydrogen bonds’ network was established. The opinion was expressed, that this non-relaxation transition is connected with a reversible collapse of PVA polymeric networks at the change of temperature in the region of the electrical forces activity, due to the presence in PAA macromolecules of ionized carboxyl groups and counterions. The similar structural - phase transition is revealed as well in xerogels of PVA-PAA graft copolymer, which temperature position is determined of interior structure of its hydrogen bonds. For PVA-PAA in the region of low temperatures the b - relaxation process of polar hydroxyl groups of its polyvinyl chains is shown also.
PROPERTIES OF POLY(VINYL ALCOHOL) - POLY(ACRYLAMIDE) GRAFT COPOLYMERS DEPENDING ON THE GRAFT LENGTHS.
3. BENZENE SOLUBILIZATION BY SOLUTIONS OF THE COPOLYMERS
N. ZAGDANSKAYA a, L. MOMOT a, T. ZHELTONOZHSKAYA a,
J.-M. GUENET b, V. SYROMYATNIKOV a
a Kiev Taras Shevchenko National University, 64, Vladimirskaya str., 01033, Kiev, Ukraine. E-mail: nzagdanska@mail.ru.
b Institut Charles Sadron CNRS UPR 22 6, rue Boussingault
F-67083 STRASBOURG Cedex France
The peculiarities of macromolecular arrangement of poly(acrylamide) to poly(vinyl alcohol) graft copolymers (PVA-PAAN), which are characterized by the equal quantity (N=9), but various molecular weight (or length) of grafted chains, in comparison with macromolecules of individual PAA and PVA, were investigated in aqueous medium.
By methods of benzene solubilization and UV spectroscopy two-step character of benzene binding in PAA solutions connected with aggravation of the thermodynamic solvent quality in the solubilization process, was established. The gradual growth of benzene binding by PVA macromolecules stipulated by the formation of hydrogen bonds with the p -electronic system of benzene molecules was marked. The presence of the advanced hydrophobic areas in a series of graft copolymers was established. It was shown, that in some region of the molecular weight alteration of grafts (from 3.72× 105 up to 4.3× 105) solubilizing ability of PVA-PAAN remains practically invariable. However, at further growth of PAA molecular weight up to 5.1× 105 it is considerably increased. The analysis of UV spectrum changes of benzene-water solution at the presence of copolymer with maximal length of grafts showed, that the marked effect is stipulated by increase of benzene binding with PVA-PAAN macromolecules through hydrogen bonding. The obtained results are discussed from the point of view of the structure modification of intramolecular polycomplexes (IntraPC), which exist in macromolecules of given copolymers, in dependence on the length of grafted chains.
The alterations of PVA-PAAN solubilizing ability as the function of temperature were also investigated. It was shown, that the rise of temperature from 281 up to 313 K results in sharp lowering of quality of bound benzene that is stipulated by the change of thermodynamic quality of a solvent and by the destruction of IntraPC structure.
POLYMER-COLLOID COMPLEXES IN THREE-COMPONENT SYSTEM: POLY(STYRENE-CO-MALEIC ACID) - POLY(ETHYLENE OXIDE) - SILICA SOL IN AQUEOUS MEDIUM
N. PERMYAKOVAa), T. ZHELTONOZHSKAYAa), N. STRELCHUKb),
N. ZAGDANSKAYAa), L. MOMOTa) , V. SYROMYATNIKOVa)
a) Kiev Taras Shevchenko National University, 60, Vladimirskaya str., 01033, Kiev,
Ukraine. E-mail permyakova@ukr.net
b) Institute of Nuclear Physic of NAS of Ukraine
47 Nauki Ave., 01028, Kiev, Ukraine
The reactions of complex formation in a solution between polymer macromolecules and smallest colloid particles are widely studied during last years. Due to the application of polycomplexes for regulation of stability of dispersed systems researches of the complex formation in multicomponent polymer-colloid systems, which components interact with each other, are of special interest. In the present work the complex formation in the model three-component polymer-colloid system, including poly(styrene-co-maleic acid), poly(ethylene oxide) and silica sol (PSMA+PEO+SiO2), in water as function of PEO molecular weight and of the order of component mixing, were considered. The state of corresponding two-component systems was studied too.
By the methods of potentiometric titration, viscometry, IR spectroscopy and benzene solubilization it was established, that in PSMA+PEO system the polycomplex composition, the degree of binding of PSMA links and free energy of complex formation, increase with growth of PEO molecular weight. It was shown, that the main factor of stabilization of the polycomplex structure are hydrogen bonds. In PSMA+SiO2 and PEO+SiO2 systems the formation of polymer-colloid complexes results in the swelling of polymer macromolecules, which appears most significant for PEO. It was shown, that the free energy of complex formation PSMA with SiO2 particles is lower, than with PEO macromolecules. In IR spectrum of polymer-colloid complex PSMA+SiO2 the new band of n C=O vibrations at 1696 cm-1 stipulated by H-bonds between PSMA and SiO2, have been detected.
The condition of three-component polymer-colloid system is independent on the order of PSMA and PEO adding, if the second polymer component is introduced at the end. In the case, when the last introduced component is SiO2 particles, the considerable increase of free energy of stabilization of three-component polymer-colloid complexes, was observed. Results of researches are discussed from the point of view the difference in energy of pair interactions.
SPECIFIC CONFORMATIONS OF POLY (VINYL ALCOHOL) -GRAFT-POLY (ACRYLAMIDE -CO-ACRYLIC ACID) IN AQUEOUS SOLUTIONS
T. VITOVETSKAYAa, T. ZHELTONOZHSKAYAa, N. STRELCHUKb,
L. KUNITSKAYAa, V. SYROMYATNIKOVa
a Kiev Taras Shevchenko National University, Faculty of Chemistry,
60 Vladimirskaya str. 01033. Kiev. Ukraine. E-mail: vitovetskaya@ukr.net
b Institute of Nuclear Physic of NAS of Ukraine
47 Nauki Ave., 01028, Kiev, Ukraine
On the basis of graft copolymers of poly(acrylamide) to poly(vinyl alcohol) (PVA-PAAm)N the new graft copolymers PVA-(PAAm-co-PAAc)N which contain a different quantity of acrylic acid links, were obtained. They belong to intramolecular polycomplexes (Intra PC) and are high efficient sorbents and binders in a solution.
In the present work some properties of this copolymers, having a constant length of the main and grafted chains (MvPVA=9.4× 10-4; MvPAAm-co-PAAc=1.68× 105), a constant quantity of grafts (N=9), were investigated in dependence on the amount A of acrylic acid links (from А=0.8 to 65.8 w %). It was shown, that macromolecules PVA-(PAAm-co-PAAc)N possess a compact structure in aqueous solution. The copolymer solubility in water is gradually reduced with growth A, but at A value more than 57,7 w % the copolymer macromolecules lose their solubility in water at all. It was established by the method of potentiometric titration that before some critical value A (near 32 w %) the process of destruction of the copolymer compact structure at the ionization of carboxylic groups proceeds gradually. However, at А value more than Аcritic this process proceeds as a sharp conformational transition such as globule-coil. The parameters of a compact and coil-like conformations as well as a standard free energy of the conformational transition, were determined. It was shown, that for dissolution of PVA-(PAAm-co-PAAc)N in water at a large A values it is necessary to achieve a definite degree of ionization of carboxylic groups, which appears the above, than more value А.
By the method of IR spectroscopy and computer separation of strongly overlapped bands in the range of u C=O vibrations of amide and carboxylic groups different structures of hydrogen bonds and also the distribution of both types of groups between such structures at A change, were established.
ION CONDENSATION ON A CHARGED FLEXIBLE POLYMER
lsabelle Morfina, Ferenc Horkayb, Francoise Bleyc, Cyrille Rochasa, Anne-Marie Hechta, Erik Geisslera
aLaboratoire de Spectrométrie Physique CNRS UMR5588, Université Joseph Fourier de Grenoble, B.P.87, 38402 St MARTIN D'HERES Cedex, France,
bSection on Tissue Biophysics and Biomimetics, Laboratory of Integrative and Medical Biophysics, NICHD, National Institutes of Health, 13 South Drive, Bethesda, MD 20892, USA
cLaboratoire de Thermodynamique et Physico-Chimie Métallurgiques, Institut National Polytechnique de Grenoble, BP 83, 38000 Grenoble, France
The interactians between mobile ions and charged macomolecules govern a variety of phenomena ranging from simple ion exchange and drug delivery systems to complex biological processes. In polyelectrolytes, the two divalent ions calcium and strontium both display similar reversible behavior with respect to monovalent ions exchange. Anomalous small angle X-ray scattering is used to determine the distribution of divalent (strontium) ions in a neutralized polyelectrolyte (sodium polyacrylate) gel. These measurements yield information simultaneously on the distribution of ions and of the polymer within the gel. The experiment revealed that the strontium is confined on the polymer backbone. No diffuse ion cloud is observed. Small angle neutron scattering (Fig.1) was used to verify independently that the signal from the polymer is not perturbed by the ion distribution.
Figure 1 : SANS and SAXS data for a sodium polyacrylate gel in presence of 40 mM NaCl and 1 mM SrCl2
Crystalization and melting of silica filled PEO: interfacial effects
S.SAid, Y.Grohens.
Université de Bretagne-Sud, L2P, BP 92116, F-56321 Lorient Cedex, France
Although many fundamental and experimental works have been dedicated over the past years to crystallisation of polymers at interfaces, the subject still requires further insights. Many significant parameters such as adsorption strength, local or global conformation or mobility (local or reptation) of polymer chain may influence the intermolecular organization near surfaces.
DSC investigations were carried out in the range of 20 to 80°C on medium molecular weight PEO adsorbed on silica particles from solution. Various polymer/silica ratio, solvent nature, surface chemistry or specific surface were studied. The key idea of this work is to tune the conformation of the adsorbed chains in order to observe the modification induced in the crystallization or melting regime.
The first observation is that for low normalised adsorbed PEO/silica ratio (below 10 w/w) the crystallization temperature (Tc) decreases as well as the melting temperature (Tm). We infer this result to the reduction of mobility of adsorbed PEO chains when large surface area of silica is available. Short loops and tails tend to hinder the organization of chain segments in crystalline lamellae. However, the normalised melting enthalpy remains constant whatever the PEO/silica ratio. This results indicates that the crystalline fraction is independent of the silica fraction. We can therefore assume that adsorption sites hinder local conformational change of macromolecular chains. These anchorage point control the crystallizable length and hence the lamellae thickness. The influence of the solvent nature, the surface chemistry and specific surface will be further discussed in the poster.
OBTAINING HIGHLY CONDUCTING POLYMERS FROM POLYANILINE SOLUTIONS
M.E.MUÑOZa , I.GONZALEZa, A.SANTAMARÍAa, J.A. POMPOSOb
aPolymer Science and Technology Department and POLYMAT, University of The Basque Country,
P.O. Box 1072 San Sebastián, Spain popmubem@sc.ehu.es
bCIDETEC Center for Electrochemical Research and Development, Parque Tecnológico de Miramón 20009 San Sebastián, Spain
The research carried out during the last decade by outstanding scientist, like Nobel Prize winners Heeger, Mac Diarmid and Shirakawa, has lead to the development of highly electrically conducting polymers with promising industrial applications. Polyaniline (PANI) is one of these intrinsically conducting polymers, which as other rigid, ”rod-like”, polymers can not be processed employing conventional methods like melt extrusion or injection. Therefore, although conductivities above 102 S/cm can be obtained with doped polyaniline, its practical use is limited by the lack of flow ability. The following routes have been proposed to overcome this severe difficulty :a) Obtaining PANI gels that melt and can be processed at elevated temperature b) Obtaining films by casting from PANI solutions c) Blending polyaniline with thermoplastic polymers.
It has been reported that gels prepared dissolving PANI in dodecylbenzenesulfonic acid (DBSA) using formic acid as a processing medium (1) or prepared dissolving camphor sulphonic acid doped PANI (PANI-CSA) in m-cresol (2), give rise to conductivities up to 3 S/cm. On the other hand, much higher conductivities (close to 150 S/cm) have been obtained in PANI-CSA films cast from m-cresol solutions, although their mechanical properties are very poor since the samples are very brittle·(3). Good processability and mechanical properties have been observed when polyaniline is mixed with thermoplastics like polistyrene or ABS terpolymer (4-5), but the conductivities are limited to a maximum of 25 S/cm.
In the present contribution we show the capacity of PANI-CSA to dissolve and form gels in other solvents, like carvacrol and thymol, besides DBSA and m-cresol. It is shown that using appropriate gel preparation conditions, thermoreversible gels of conductivities similar to brittle films (that is above 100 S/cm) can be obtained.
References:
1.- T. Vikki et al. Macromolecules 1997, 30, 4064
2.- O.T. Ikkala et al. Mat.Res.Soc.Symp.Proc. 1998, 488, 377
3.- O.T. Ikkala et al. J. Chem. Phys. 1995, 103,9855
4.- R.C. Patil et al. J.Polym.Sci. Part A 1999, 37, 2665
5.- M. Zilberman et al. J. Macro. Sci. Phys. 2000, 39,333
VISCOELASTICITY AND MORPHOLOGY OF POLYANILINE GELS
M. VECINOa , M.E. MUÑOZa , I. GONZALEZa, A. SANTAMARÍAa, J.A. POMPOSOb
aPolymer Science and Technology Department, University of The Basque Country,
P.O. Box 1072 San Sebastián, Spain qpbvevem@sc.ehu.es
bCIDETEC Center for Electrochemical Research and Development, Parque Tecnológico de Miramón 20009 San Sebastián, Spain
A new method to prepare camphor sulphonic acid doped polyaniline PANI(CSA)/m-cresol solutions, allow us to obtain highly conducting gels of polymer concentration up to 60%. In the present contribution the viscoelastic properties of these gels are analysed. It is observed that the elastic modulus Ge of the gel, defined as a value of the storage modulus, G´, independent of frequency and temperature, scales with polymer concentration as Ge µ c2. An exponent value of 2 can be interpreted as the expression of a rod structure, according to the model of Jones and Marqués (J.Phys. France 1990,51,1113).The network can be observed using a Scanning Electron Microscope with vacuum dried gels: Coating with gold is not necessary, due to the conductivity of the sample. In Figure 1 a fibrillar morphology is clearly noticed. The fibril diameter is about 50nm. The typical viscoelastic response of a gel vanishes at high temperatures giving a viscous dominant behavior. On cooling, the gel response is recovered, showing the thermoreversibility of the network.
FORMATION OF POLY(ETHYLENE GLYCOL) INCLUSION COMPLEXES IN AQUEOUS SOLUTIONS OF MIXED CYCLODEXTRINS
J. HORSKÝ, Z. WALTEROVÁ
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského sq. 2, CZ-162 06 Prague 6, Czech Republic
email: horsky@imc.cas.cz
In the last decade, inclusion complexes between cyclodextrins (CDs) and polymers have attracted great attention. The complexation in solution is usually accompanied by precipitation, and a solid complex is obtained in a high yield, as is the case of poly(ethylene glycol) (PEG) and a -CD (six glucose units); however, the process is strongly specific as no precipitation by PEG is observed with a -CD derivatives or with unmodified or modified b -CD (seven glucose units). This led to the assertion that cooperative interactions between cyclodextrin molecules threaded on the same PEG chain are the driving force of the complexation. Recently, however, low solubility of the complex rather than strong complexation was suggested as a source of high-yield precipitation and, at the same time, indications were obtained that complexation between CDs and PEG can occur in solution even if no precipitation is observed. Finding that (2-hydroxypropyl)-a -cyclodextrin (HPACD) promotes the evolution of turbidity in solutions of a -CD initiated our investigation of precipitate formation in aqueous solutions of PEG and a CD alone and in combination with HPACD, b -CD, and (2-hydroxypropyl)-b -cyclodextrin (HPBCD), i.e., with CDs which individually do not produce precipitates with PEG. In all cases, addition of these "non-precipitating" CDs did not alter (within experimental error) the amount of precipitated complex, which depended only on the amount/concentration of the a -CD present. A model of an array of independent binding sites, which adequately describes equilibrium properties of complexes in which several host molecules is threaded on a chainlike guest molecule, is used to show that the above results not necessarily imply the absence of inclusion complexation between PEG and "non-precipitating" CDs. Sch complexation would be possible if a low solubility of the PEG/a -CD complex is the driving force of its precipitation.
The project is supported by the Grant Agency of the Academy of Sciences of the Czech Republic (Grant #A1050101/01).
New class of composite nanomaterial by encapsulation
S. Poux, A. Thierry, J.M. Guenet,
Institut Charles Sadron CNRS UPR 22, 6, rue Boussingault F-67083 STRASBOURG Cedex France, Sandrine.Poux@ulp.u-strasbg.fr
We report on a new type of composite material where the filaments of a self-assembling bicopper complex are encapsulated in polymer na-nowires 1. The encapsulation is achieved within the fibrils of thermoreversible gels. Two systems have been studied:
-Isotactic polystyrene / copper II 2-ethylhexanoate / trans-decalin
In this ternary system, the self-assembled bicopper complex has been shown to act as a heterogeneous one-dimensional seed for nucleating the growth of the fibrils of iPS thermoreversible gel 2.
-Polyhexylisocyanate / copper II-ethylhexanoate / Octane
Here, optical microscopy observation have no detected any rejection of the bicopper complex into the solvent imbedding the fibrils of the gel 3. Other results show that the encapsulation of filament of bicopper complex can be achieved through the formation of a solid solution.
Characterization by differential scanning calorimetry, by small-angle neutron scattering and by mechanical measurements will be presented. The morphological aspect will be shown too.
References:
1) R.L. Martin, H. Waterman J. Chem. Soc. 1957 2545
P. Terech, P. Maldivi, J.M. Guenet, Europhys. Lett. 1992 17, 515
2) D. Lopez, J.M. Guenet Eur. Phys. J. B 1999 B12 405
3) S. Poux, A. Thierry, N. Fazel, A. Dahoun, J.M. Guenet, Macromol. Symp. 2001 168, 67
HYDRATION OF POLYMERS CONTAINING AMIDE GROUPS INVESTIGATED BY INFRARED AND RAMAN SPECTROSCOPY AND DFT CALCULATIONS
J. DYBAL, P. SCHMIDT
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovský Sq. 2, 162 06 Praha 6, Czech Republic
The role of hydration of polymer segments has been studied for two types of amide polymers undergoing inverse temperature transition in an aqueous solution near room temperature: elastin-like poly(pentapeptide)s represented by poly(GVGVP) and poly(AVGVP), with amide groups in the main chain, and poly(N-isopropylacrylamide), with amide groups in the side chain.
Analysis of temperature and concentration dependences of the infrared and Raman spectra has shown that the studied polymers exhibit vibrations sensitive to both changes in the conformational structure of the main chain and local changes in the environment of the polymer chain caused by hydrophobic or hydrophilic interactions (C-H stretching). The observed frequency shifts of the C-H stretching vibrations are predominantly caused by blue-shifting hydrogen bonds C-H...OH2. The experimental findings have been correlated with the DFT calculations of the vibrational frequencies and infrared and Raman intensities at the B3LYP/6-31G(d) and B3LYP/6-311+G(2d,p) levels for a series of small model structures of amide polymers surrounded by a growing number of water molecules, from one water molecule to a clathrate-like structure.
Contact angles on gel-like polymer surfaces in water : a route to the understanding the antifouling activity ?
Y. Grohens, S. Ulvé, K.Vallée-Réhel, J.J.Péron, D. Haras
Université de Bretagne-Sud, LBCM (EA 2594), BP 92116, F-56321 Lorient Cedex, France
The evolution of the international, environmental legislation is moving towards a total withdrawal of organotin compounds and to a severe limitation of the use of cuprous oxide and of organic molecules in antifouling paints. To develop new antifouling strategies without added toxic products, it is necessary to further understand the phenomenum of bioadhesion in relation with polymers surface characteristics. Erodable paints are blends or copolymers enclosing hydrophilic, hydrophobic and hydrolysable units. In contact with water this polymeric systems exhibit a very complex surface structure (hydration, association between hydrophobic sequences, hydrolysis, appearance of polyelectrolyte sequences, segregated domains) which can be compared with a gel-like structure.
Contact angle measurements (captive bubble and sessile drop technique) were used to determine the surface energy of several polymers (based on acrylic, organotin or acid lactic monomers) at the early stage of immersion (T0) in pure water and salt water or after several days (Tx). The sessile drop technique using various liquid probes allows the calculation of the dispersive, acid and basic component of the surface energy. Significant differences in the surface energy are observed between the polymers at T0 and tend to be lowered after immersion along with a general increase of the surface energy. The same trend is observed by the ‘’in-situ’’ captive bubble technique (q drop = p - q bubble). The surfaces become more hydrophilic with a final contact angle, q bubble, of 140 ± 10° in pure water and 150± 4° in 0,15 M salt water. The exact meaning of these modifications of surface energy between T0 and Tx is still unknown. One assumption is that the important degree of swelling of the immersed surface layer is a significant factor in the surface measured thermodynamics. However, since all these polymers do not exhibit the same anti-fouling activity, further factors such as the elasticity of the polymer network and the structure of the gel should be taken into account.
EXPERIMENTAL DETERMINATION OF THE FIRST SOLVATION SHELL OF MACROMOLECULES
JINDŘICH HAŠEK, JAN DOHNÁLEK, JARMILA DUŠKOVÁ
Laboratory of Molecular Structure, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic, hasek@imc.cas.cz
Interaction of solvent with surface of macromolecule and its penetration in cavities formed between folded chains have very significant role in the global 3-D structure of macromolecular complexes. Combination of three methods 1) molecular dynamics, 2) NMR spectroscopy and 3) X-ray crystallography is necessary to describe the problem in its complexity. Molecular dynamics can give partial answers concerning the dynamic and entropy of the whole system, NMR is able to describe frequency of mutual interchange of water molecules in solvating shell. The X-ray structure analysis, stressed here, gives a detailed description of well localized sites around the macromolecule in which solvent molecules interchange.
This paper shows tests performed on 107 independent structure X-ray experiments with different HIV protease complexes. The results show high reliability of determination of water sites. Solvent molecules in direct contact with surface of macromolecule (in the first hydrating shell) have usually well defined positions. Namely, water sites in grooves, forming hydrogen bond networks, are defined comparably well as they were part of molecule.
Acknowledgement: GA CR no. 204/02/0843/A and no.203/02/0436/A
Abstract not supplied.
Evaluation of the Fractionated Crystallization of Isotactic Polypropylene and High Density Polyethylenes in their Blends with Cycloolefin Copolymers
Sylvie Pimbert, Yves GROHENS
Laboratoire Polymères & Procédés, Université de Bretagne Sud, BP 92116 - 56321 Lorient, France
Miscibility and crystallization of semi-crystalline polyolefins (i-polypropylenes and HD-polyethylenes) in their blends with amorphous cycloolefin copolymers (COC) have been evaluated by Differential Scanning Calorimetry (DSC).
In i-PP–COC blends, no evolution of PP melting point and COC glass transition temperature is observed, corresponding obviously to immiscible blends. Fractionated crystallization appears when i-PP is finely dispersed in the COC matrix (i-PP contents below 30% w/w). Such a behavior is generally observed when the number of PP droplets is much larger than the number of heterogeneities originally present in the bulk polymer.
HDPE–COC blends show a significant decrease of both PE Tm and COC Tg, characterized by both DSC and DMA. Such observations are usually associated to some polymer miscibility in the amorphous phase.
A fractionated crystallization process is also observed in these blends and seems directly correlated not only to the COC content but also to the PE molecular weight. The unusual crystallization of a high MW HDPE is limited to about 50 % of the total amount.
A determination of the droplet concentration and particle size distribution was performed in these blends through morphological observations by Scanning Electronic Microscopy (SEM). The nucleation and crystallization modes are largely influenced by the characteristics of the micro-dispersed phase.
SOLVENT INDUCED CRYSTALLIZATION IN SYNDIOTACTIC POLYPROPYLENE
G. GORRASI, L. GUADAGNO, V. VITTORIA
Department of Chemical and Food Engineering, University of Salerno, via Ponte don Melillo, 84084 Fisciano (Salerno)-Italy-
It has long been known that polymer-solvent interaction is a possible route for obtaining crystallization. The basic mechanism of solvent induced crystallization (SINC) is very much the same as that of thermal induced crystallization from the glassy state since both involve, as a necessary step, the inducement of segmental mobility. The former achieves the goal by use of "chemical energy", and the latter does so by use of thermal energy. Moreover, in the case of SINC, the solvent polymer interactions may differ in degree from solvent to solvent, so that the obtained crystallinity and the morphological texture can vary, and the final properties may be manipulated by the choice of solvent. Most of the studies in this field dealt with systems initially in the amorphous or glassy state. Highly stereo and regio-regular syndiotactic polypropylene (sPP) is a recently synthesized polymer. Due to its very complex polymorphism and new properties it is attracting a great interest both from industry and academia. Although the thermodynamic stable crystalline form shows the chains in helical conformation, when sPP sample, after melting, is kept in a bath at 0°C for long time, it spontaneously crystallises in a trans-planar form. This novel form was interpreted as a mesophase containing lateral disorder in the packing of the trans planar chains. This new form can crystallize into the most stable helical form either by thermal treatments or by solvent interaction. In this work we report the analysis of the sorption phenomena and the SINC of trans-planar mesophase of sPP using solvents with different solubility parameters, (cal/cm3)1/2. The solubility parameter of the polymer, corresponding to the solubility parameter of the solvent with which it has the maximum interaction, is useful in predicting the swelling behaviour; in our case the treatment of such polymer with solvents can help to better clarify the structural and morphological transformations occuring in the sPP mesophase.
STARCH SWELLING AND ITS ROLE IN MODERN CERAMIC SHAPING TECHNOLOGY
E. TÝNOVÁ, W. PABST, J. MIKAČ
Department of Glass and Ceramics, Institute of Chemical Technology Prague, Technická 5, CZ-166 28 Prague 6, Czech Republic
In traditional ceramic technology starch has been used as a pore-forming agent for a long time. In that application, starch is added to the as-prepared aqueous suspension or paste, and shaping is performed by classical isothermal procedures (slip casting into porous molds, extrusion). The negligible swelling of most natural starch types at, or slightly above, room temperature allows the preparation of ceramic green bodies with precisely controllable microstructure (e.g. porosity and pore size). Recently, however, a new ceramic shaping process has been developed, in which starch is used not only as a pore-forming agent, but also as a body-forming agent. This second function is based on the ability of starch to undergo irreversible swelling at moderately elevated temperatures (<100 °C) and to give rise to in-situ drainage of aqueous suspensions. Concomitantly, supported by partial dissolution of the amylose and amylopectin units, the originally aqueous matrix is transformed from a purely viscous suspension to a visco-elastic gel. With this generic method, which has already been applied to various systems of silicate, oxide and non-oxide ceramics, net shaping of ceramic green bodies is possible by slip casting into nonporous (e.g. metal or polymer) molds.
In this work a microscopic real-time visualisation of potato starch swelling in aqueous media at elevated temperature (56 °C) is performed with the help of a specially constructed optical flow-through cell connected with a thermostat.
The phase transxtxon of viscous starch-water mixtures into a visco-elastic gel is documented by viscometric measurements in the shear and oscillation mode.
Starch swelling kinetics are measured by low-angle laser light scattering ("Fraunhofer diffraction") of starch suspensions previously heated (in a laboratory drier at 80 °C) and then suddenly quenched to approx. 20 °C in the sampling volume of the laser granulometer. Results can be fitted with a four-parameter equation, which can serve to predict the minimum time necessary for ceramic green body formation, when a simple geometric (steric) model (based on an idealized ceramic suspension with spherical particles) is adopted.
DYNAMIC PROPERTIES OF PROTEIN-LIKE heteropolymers.
A COMPUTER Simulation STUDY
JOANNA KACAK, ANDRZEJ SIKORSKI, PIOTR ROMISZOWSKI
Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland
The simple model of a single polypeptide chain was used in the computer simulation. The units in a model polypetide (amino acid residues) were located at carbons and embedded to a very flexible [310] lattice. The force field that mimic the polymer-polymer and polymer-solvent interactions contained the long-range contact potential between the residues as well as the local preferences in forming helical structures. The chain consisted of two types of residues: hydrophillic and hydrophobic. The classical Metropolis simulation algorithm was used.
Monte Carlo simulation were carried out for some model sequences of residues and for various temperature conditions. It was shown that the formation of secondary structures in the chain under consideration had the influence on the local short-time dynamic properties. The analysis of the autocorrelation functions enables one to identify the presence of secondary structures. The analysis of the formation of polymer-polymer and polymer-solvent contacts in ordered structures was also made.
LOCAL ORDERING in PROTEIN-LIKE heteropolymers.
A MONTE CARLO SIMULATION
ANDRZEJ SIKORSKI, PIOTR ROMISZOWSKI
Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland
The lattice approximation of a heteropolymer chain as a model of a single polypeptide was used in the computer simulation. The residues of a model polypetide were represented by the chain of carbons located on a very flexible [310] lattice. The force field that mimic the polymer-polymer and polymer-solvent interactions contained the long-range contact potential between the residues as well as the local preferences in forming helical structures. The chain consisted of two types of residues: hydrophillic (P) and hydrophobic (H), forming a typical repeatable unit –HHPPHPP-. The simulations were performed by means of the Replica Exchange Monte Carlo method combined with the Histogram Method.
The series of simulations were carried out enabling one to investigate the influence of both components of the force field on the transition temperature and the characteristics of the coil-to-globule transition. The properties of low-temperature ordered structures were determined. The thermodynamical description of the model chain was also given. The phase transition was found to be sharp and cooperative for longer chains and strong helical potential.
A novel pH sensitive porous membrane carrier for various biomedical applications based on pHEMA/chitosan: preparation and its drug release characteristics
Gülay Bayramoğlu1 and M. Yakup Arica2*
1Department of Chemistry, Kırıkkale University, 71450 Yahºihan Kırıkkale, Turkey
2Department of Biology, Kırıkkale University, 71450 Yahºihan Kırıkkale, Turkey
During the last decade, a steadily increasing attention has been paid to synthetic and natural polymer hybrid materials due to a wide range of potential applications. The suitable biomaterials for biomedical applications include poly(hydroxyethyl methacrylate), (pHEMA), and chitosan. The synthetic hydrogels based on pHEMA have been widely studied and used in biomedical fields. Chitosan, 1-4-2amino-2deoxy-b-d-glucan, is a polysaccharide obtained from chitin by deacylation process. Chitosan is a natural polycationic polymer that possesses useful properties such as non-toxicity, high biocompatibility and non-antigenicity that offer advantages for possible clinical uses (1).
Equilibrium swelling studies were conducted to investigate swelling behaviours of the membrane according to the pH of the swelling medium. The swelling properties of the membrane was changed with the medium pH. The equilibrium water uptake is reached in about 60 min. Compared with pHEMA (58%), the water-swelling ratio of the pHEMA/chitosan membrane increased significantly (69%). Several factors could contribute to this result: (i) incorporation of chitosan into pHEMA network introduced more hydrophilic functional groups (i.e., -NH2 and –OH), (ii) presence of chitosan macromolecules in the polymerisation mixture could effectively decrease the molecular mass of pHEMA and reduce the crystallinity (2). As a results, the water molecules penetrate into the polymer chains more easily, resulting in an improvement of pHEMA/chitosan membrane water swelling properties in aqueous solutions. The pHEMA/chitosan membrane thickness and density was measured to be 600 m and 1.26 g cm-3, respectively. The plain surface area of the 1.0 ml wet IPNs membrane was 38.5 cm2.
The presented novel pHEMA/chitosan membrane has most of the useful properties for biomedical application. For example, it is highly hydrophilic and very inert toward microbial degradation and resistance to many chemicals due to its nature of both component of the network. One of the components of the membrane pHEMA has also good mechanical strength and the porosity could be modified by varying the concentration of pore forming agent in the polymerization mixture. The scanning electron microscope (SEM) micrographs displayed a smooth, channel like, and porous surface structure. Antibiotic release experiments were also performed with amoxicillin loaded pHEMA/chitosan membrane in physiological saline solution. The membrane loaded with 100 mg antibiotic g hydrogel released around %80 of the amoxicillin in 5 h at pH 7.4. The presented well characterised novel pHEMA/chitosan membrane is a potential candidate for antibiotic carrier or a support in bio-separation.
Dye-ligand immobilized IPN membrane for removal heavy metal ions
Gülay Bayramoğlu1, Ömer Genç2 and M. Yakup Arica3*
1Department of Chemistry, Kırıkkale University, 71450 Yahºihan Kırıkkale, Turkey
2Department of Chemistry, Kırıkkale University, 71450 Yahºihan Kırıkkale, Turkey
3Department of Biology, Kırıkkale University, 71450 Yahºihan Kırıkkale, Turkey
The abilities of various sorbent materials for heavy metal removal have been reported in the literature [1]. We have developed a novel approach to obtain high metal sorption capacity utilizing a membrane containing chitosan and an immobilized reactive dye (i.e. Procion Yellow H-E3G). Poly(hydroxyethyl methacrylate)/chitosan composite membrane were prepared by UV-initiated photo-polymerisation of HEMA and chitosan in the presence of an initiator azobisisobutyronitrile. It was then the reactive dye was immobilized on the composite membrane under alkaline condition. The composite membrane were characterised by swelling studies, scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. These membrane have small pores: the micro-pore dimentions are approximately 5-10 m. The composite membrane with a swelling ratio of 76%, the HEMA:chitosan ratio was 50:1 and the dye-ligand loading was 87 mol g dry membrane-1. The membrane were used in the removal of heavy metal ions of copper, cadmium and mercury from aqueous media containing different amounts of these ions (5-600 mg l-1) and at different pH values (2.0-7.0). The maximum adsorption capacities of heavy metal ions onto the composite membrane unde non-competitive conditions were 35.3 mmol m-2 for Cu(II), 39.6 mmol m-2 for Cd(II) and 52.7 mmol m-2 for Hg(II). The affinity order was Hg(II) > Cd(II) > Cu(II). The adsorption of heavy metal ions increased with increasing the medium pH and reached a plateau value at approximately pH 5.0. Desorption of heavy metal ions was performed using 0.1 M HNO3 and the composite membrane was suitable for more than five cycles without noticeable loss of capacity.
[1]. A. Denizli, R. Say, and M. Y. Arica, Sep. Sci. Technol. 34 (1999) 2369.
Structure Analysis of Liquid-Crystalline Polymers. Modeling and Experiment.
J.Repákováa, P. Čapkováa, M. Studenovskýb, M. Ilavskýa,b
aFaculty of Mathematics and Physics, Charles University, Ke Karlovu 3, CZ-12116 Prague 2, Czech Republic
bInstitute of Macromolecular Chemistry, Academy of Sciences, CZ-16206 Prague 6, Czech Republic
Liquid crystalline polymers (LCPs) are widely studied due to their versatile physical and chemical properties, such as thermal stability, electro-activity, non-linear optical activity etc. The liquid crystallinity is associated with ordering of polymer chains which are stiffer than those in amorphous polymers. The stiffness and strength of polymer chains are of central importance and are usually achieved by increasing content of stiff (mesogenic) groups in the molecules. In thermotropic LCPs the LC phase exists only within a particular temperature range. To set up the LC phase into a reasonable broad temperature range is one of the primary objectives in the design of LCPs.
Present work deals with the side-chains LC polyuretanes prepared from LC diols (based on diethanolamine derivatives) with mesogenic groups of various structure in the side chain and two diisocyanates of various flexibility; the stoichiometric ratio of reactive isocyanate (NCO) and hydroxy (OH) groups was used at synthesis of LCPs. The modelling using molecular mechanics and classical molecular dynamics was used in investigation of the LCPs structure and structure-properties relationship. Two parameters have been introduced to characterize the degree of chain deformation after molecular dynamics: the relative change of the radius of gyration of the chain rg/rg and the relative change of the chain length l/l. Preliminary results can be summarized as follows:(i) The degree of chain deformation depends on the structure of mesogen as well as on the type of diisocyanate. (ii) The characteristics describing the chain deformations calculated after 30 ps of dynamics simulations were within the interval 0.142 - 0.321 for rg/rg and 0.207 – 0.348 for l/l. The values of these characteristics for polymers with the LC phase were just in the middle of these intervals. (iii) In case of identical side chain, the degree of chain deformation and the existence of the LC phase depend strongly on the type of diisocyanate. The strong correlation has been found between the degree of chain deformation and the temperature of the transition from the crystalline to LC phase.
VISCOELASTIC BEHAVIOR OF THE ALTERNATING TERPOLYMERS OF ETHENE, PROPENE AND CARBON MONOXIDE
V.P. PRIVALKO1*, V.B. DOLGOSHEY1, E.G. PRIVALKO1, V.F. SHUMSKY1, F. HOLLMANN2 AND B. RIEGER2
1 Institute of Macromolecular Chemistry, National Academy of Sciences of Ukraine, Kharkiv Chaussee 48, 02160 Kyiv, UKRAINE
2 Department of Inorganic Chemistry II, Materials & Catalysis, University of Ulm, D-89069 Ulm (Donau), GERMANY
A series of the alternating terpolymers of ethene, propene and carbon monoxide with different Et/CO contents was characterized by storage and loss shear moduli (measured in the frequency window spanning about three decades) at several fixed temperatures in the interval from 120 to 220o C.
The bell-like plot of the reduced (i.e., molar mass-independent) values of complex viscosity vs. Et/CO mass content was quantitatively reproduced by classical copolymerization theory assuming the strictly alternating Et/CO and Pr/CO copolymers as ”virtual homopolymers” 11 and 22, and the strictly alternating (Et/CO)/(Pr/CO) terpolymer as an ”alternating virtual copolymer” 12. Compared to other flexible-chain polymers, the apparent plateau moduli for terpolymers were several-fold lower, suggesting unusually loose structure of entanglement networks. Thus, the CO groups in the main chain of terpolymers were ranked as the least effective entanglement formers, whereas the unlike diads of the type (Et/CO)/(Pr/CO) were more effective than the like diads of the type (Et/CO)/(Et/CO) or (Pr/CO)/(Pr/CO).
The systematic hysteresis effects during initial heating up to 220o C and subsequent cooling down to 120o C for samples Et/CO=30.6 and Et/CO=31.9 were regarded as experimental evidence for existence of the ordered nanodomains in the initial nanostructured state which served as reinforcing bridges for a continuous disordered matrix.
MELT VISCOELASTICITY OF POLYPROPYLENES PREPARED UNDER DIFFERENT POLYMERIZATION REGIMES
V.P. PRIVALKO A) , V.B. DOLGOSHEY, E.G. PRIVALKO AND V.F. SHUMSKY,
Institute of Macromolecular Chemistry, National Academy of Sciences of Ukraine, Kharkiv Chaussee 48, 02160 Kyiv, UKRAINE
A. LISOVSKII, M. RODENSKY AND M. S. EISEN
Department of Chemistry and Institute of Catalysis Science and Technology, Technion-Israel Institute of Technology, 32000 Haifa, ISRAEL
Four samples of polypropylene prepared under different polymerization regimes were characterized by wide-angle (WAXS) and small-angle (SAXS) X-ray diffraction, by specific heat capacity in the temperature interval from –50 to 220o C (DSC), and by linear viscoelasticity at several fixed temperatures in the interval from 120 to 220o C. Storage G’( w ) and loss G’’( w ) shear moduli in the melt state (measured in the frequency window spanning about three decades ) were treated to derive the relaxation times spectra h (t ) using the NLREG computer program based on Tikhonov’s method of non-linear regularization.
Molecular characteristics were derived from the melt viscoelastic properties of three crystallizable (isotacticity index above 95 %) PP samples exhibiting the Newtonian melt flow behavior at low angular frequencies. The anomalous viscoelastic behavior in the first heating run of the elastomeric PP in the temperature interval below ca. 170o C , combined with the relevant WAXS, SAXS and DSC data, was considered as evidence for the existence of a spatial network of microcrystallites formed by lateral aggregation of stereoregular sequences which were, however, too short for the development of chain-folded, lamellar crystals typical for semi-crystalline homopolymers. The ”normal” viscoelastic behavior during the subsequent cooling run from a structureless melt state suggested a very slow kinetics of microcrystallinity development. The results obtained demonstrate a high potential of viscoelastic measurements for structural characterization of poorly crystallizable, elastomeric polymers.
INFLUENCE OF MICROCRYSTALLINITY ON DIELECTRIC RELAXATION OF ALTERNATING TERPOLYMERS OF ETHENE, PROPENE AND CARBON MONOXIDE
V.P.Privalkoa,*, P. Pissisb, G. Polizosb, V.V. Korskanova, E.G. Privalkoa, V.Yu.Kramarenkoc, V.B. Dolgosheya, e, W. Huhnd, F. Hollmannd and B.Riegerd
aInstitute of Macromolecular Chemistry, National Academy of Sciences of Ukraine, Kharkiv Chaussee 48, 02160 Kyiv, UKRAINE
bNational Technical University of Athens, Zografou Campus, GR 15780 Athens, GREECE
cPolytechnic University, Frunze 21, 61002 Kharkiv, UKRAINE
dDepartment of Inorganic Chemistry II, Materials & Catalysis, University of Ulm, D-89069 Ulm (Donau), GERMANY
eInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic
The alternating terpolymers of ethylene, propylene and carbon monoxide were characterized by WAXS, DSC, TSDC and dielectric relaxation spectroscopy (DRS). At room temperature, the terpolymers turned out X-ray amorphous ; however, the existence of weak endothermal effects over fairly broad temperature intervals above the glass transition suggested that they should be classified as ”microcrystalline” (in a sense that the ultimate level of crystallinity lies beyond the resolution limits of ordinary WAXS instruments).
The DRS data in the temperature intervals of α- and sub-glass relaxations were quantitatively fitted to the Havriliak-Negami equation. The characteristic parameters for the α-relaxation were consistent with classification of terpolymers as extremely fragile glass formers ; however, their high fragility was attributed to steric constraints to the motion of chain dipoles by the residual network of microcrystals. Strong asymmetry of the dielectric sub-glass relaxation was regarded as the additional experimental evidence for the interference of the spatial network of microcrystallites with the motion (in this case, non-cooperative) of chain segments.
*To whom all correspondence should be addressed ; E-mail : privalko@iptelecom.net.ua
PROPERTIES OF POLY(VINYL ALCOHOL) - POLY(ACRYLAMIDE) GRAFT COPOLYMERS DEPENDING ON THE GRAFT LENGTH.
2. THERMAL PROPERTIES IN THE BULK STATE
O. DEMCHENKO a, T. ZHELTONOZHSKAYA a, J.-M. GUENET b, I. RAKOVICH a, S. PHYLIPCHENKO a, V. SYROMYATNIKOV a
a Kiev Taras Shevchenko National University, 64 Vladimirskaya str., 01033, Kiev, Ukraine. E-mail: vitovetskaya@ukr.net
b Institute Charles Sadron CNRS UPR 22 6, rue Boussingault, F-67083 STRASBOURG Cedex France
Thermal analysis methods are a powerful and effective toll to study solid-state macromolecular arrangement and are of practical importance in many polymer applications. Graft copolymers of poly(acrylamide) to poly(vinyl alcohol) (PVA-PAAN), so-called intramolecular polymer complexes (IntraPC), display a different thermal behavior when Mv PAA varying from 3.37× 105 to 5.1× 105 at constant N=9.
Thus, differential scanning calorimetry of graft copolymers showed that the complete compatibility of PVA and PAA through hydrogen bonding, is realized only in the range of the length of grafts, not exceeding some critical value (Mv PAA= 4.3× 105). At longer grafted chains phase separation occurred due to strong interaction of PAA segments on the remote distances from PVA chain. The appearance of PAA micro domains in PVA-PAAN cannot be used as criterion of thermodynamic incompatibility of polymer components, because this phenomenon is stipulated by absence of conditions for realization of thermodynamic affinity of components in such polymer systems.
The content of absorbed and trapped water in the graft copolymers determined by differential thermogravimetric analysis (DTGA), also reflects some features of PVA-PAAN structure. The thermal decomposition behavior of IntraPC on air is of special interest. The first decomposition region begins at higher temperature together with N length growth. Formal-kinetic decomposition parameters (E, n, Z and k) of the distinct weight loss regions were determined simultaneously by means of computer processing of TG and DTG data with applying of modified kinetic equation in complex with least quadrates method. For the first decomposition stage they appear to be the greatest in the case of the sample with the largest quantity of hydrogen bonds between the main chain and grafts (Mv PAA = 4.3× 105). The mechanism of thermal decomposition of PVA-PAAN as a function of PAA length will be suggested. Discussion of presented investigations will bring some new understanding to the peculiarities of IntraPC.
CONDUCTIVE POLYMER COMPOSITES (CPC): MECHANICAL AND RHEOLOGICAL PROPERTIES AND MODIFICATIONS INDUCED BY CARBON BLACK PARTICLES INTRODUCED INTO SINGLE-PHASE CONDUCTIVE POLYMER COMPOSITES, EEA-CB AND PEBAX-CB
J. F. Feller, I. Linossier, G. Levesque
Laboratoire Polymères & Procédés, Université de
Bretagne Sud,
Rue de Saint-Maudé, 56 325 Lorient, France
Carbon black (CB) filled poly(ethylene-co-ethyl-acrylate) (EEA-CB) and poly(oxytetramethylene-co-amide11) (PEBAX-CB) are used for conductive polymer composites (CPC) design and lead to smart properties for heating applications. As electrical conductivity of the CPC results from the CB particles percolation, dispersion mechanisms of CB during the extrusion process or heating/cooling cycling are important parameters to study and control.
The small scale at which CB particle aggregation/dispersion phenomena take place within the CPC, make direct observation difficult. But carbon black particles/polymers interactions are responsible for several other CPC properties modifications, which allow indirect characterisation of the phenomenon. It has already been shown that the affinity of CB for acrylate functions of poly(ethylene-co-alkyl acrylates) could modify its crystallisation and that CB concentration at the interface between two polymers in diphasic systems leaded to a decrease in resistivity.
The present study is dedicated to the observation of mechanical and rheological properties modifications induced by carbon black particles introduction in two monophasic conductive polymer composites, EEA-CB and PEBAX-CB. A strong reinforcing effect of the CPC by CB in both solid and liquid states has been noticed. This phenomenon has been analysed in terms of interactions and mobility of macromolecules and carbon black particles as a function of temperature and CB content. Most of CPC relaxations are shifted to higher temperatures with increasing CB content. Results have been interpreted with models presented in the literature and confirm the necessity for CPC rheology control especially during the process to allow electrical properties reproducibility.
EFFECT OF SHEAR RATE AND TEMPERATURE ON CARBON BLACK DISTRIBUTION IN POLY(BUTYLENE TEREPHTHALATE) / POLY(ETHYLENE-CO-ETHYL ACRYLATE) BLENDS EVALUATED BY ELECTRICAL MEASUREMENTS.
I. Linossier, J. F. Feller
Laboratoire Polymères & Procédés, Université de
Bretagne Sud,
Rue de Saint-Maudé, 56 325 Lorient, France
Blends of poly(butylene terephthalate) / poly(ethylene-co-ethyl-acrylate) / carbon black (PBT / EEA-CB) lead to conductive polymer composites (CPC) with smart properties for heating applications. CB is initially dispersed in EEA to constitute the conductive phase whereas PBT provides the system with both thermal stability and mechanical properties. Although the positive temperature coefficient (PTC) is lowered by PBT thermal expansion, no negative temperature coefficient (NTC) can be observed up to 170 °C, temperature over which PBT begins to melt. To guaranty the reproducibility of electrical properties of such materials, it is necessary to control every influential parameter. We have already investigated the role of carbon black during poly(ethylene-co-alkyl acrylates) crystallisation and the influence of composition on electrical properties. The relation between processing conditions and electrical properties of CPC is an important point that has already been studied by some authors. Nevertheless, it appears that the influence of parameters such as processing temperature, shear rate and blending time depend on the considered techniques and polymer systems. For monophase systems, increasing mixing time or mixing speed increases resistivity as a result of a better conducting particles dispersion. For multiphase systems the previous parameters can lead to the opposite behaviour such as the migration of conducting particles to the interface between the two polymers, leading to a decreases of resistivity. The effect of an increase of blending temperature is generally to favour particle agglomeration in the melt and to decrease resistivity. We have found that for extruded tapes of PBT / EEA-CB, an increase of both mixing temperature and apparent shear rate leads to a decrease of resistivity.
STRUCTURAL STUDIES OF THE SYNDIOTACTIC POLYSTYRENE / ETHYLBENZENE COMPLEX
S.J. SPELLS and S. MOYSES
Materials Research Institute, Sheffield Hallam University, City Campus, Sheffield S1 1WB, U.K.
Studies of the syndiotactic polystyrene / ethylbenzene (sPS/EB) complex, using a range of physical techniques, provide an insight into the structure of the various phases formed and the nature of the phase transitions. Neutron scattering measurements show the lamellar δ (complex) phase, as obtained from solution crystallisation, to involve a sheet arrangement of crystal stems along the crystallographic a direction(1). Computer modelling enables estimates to be made of chain folding parameters, such as the "cluster size". Decomplexation involves a temporary disordering, as evident from FTIR measurements, and an increase in the X-ray long period, before the solvent-free γ phase is formed(2). For sufficiently high molecular weights, neutron scattering measurements on tilted samples indicate the occupation of two lamellae by a single molecule in both δ and γ phases.
(1) S. Moyses and S.J. Spells Polymer 39, 3665 (1998)
(2) S. Moyses and S.J. Spells Polymer 39, 3537 (1998)
Photo-Ageing of a Thermoplastic Aromatic Polyurethane in Contact with Artificial Sweat
C. Dubois 1, J. Vebrel 2, V. Rigny-Bourgeois1
1 EA 473 «Microanalyse des Matériaux » LRC CEA MO7, UFR ST, 16 route de Gray, F-25030 Besançon Cedex, France, claude.dubois@univ-fcomte.fr
2 Laboratoire de Chimie des Matériaux et des Interfaces, UFR ST, 16 route de Gray, F-25030 Besançon Cedex, France
An artificial photoageing cell was adapted in order to study the behaviour of polymers partly immersed in artificial sweat. The goal was to select a polymer and to transform it into an object that would be in contact with the skin. The polymer studied in this paper is a thermoplastic aromatic polyurethane with particularly characteristics: supple, transparent, lightly yellow colored and hypoallergenic. The ageing of this TPU was studied with or without the presence of light stabilizers.
The physico-chemical degradation of the TPU was analysed step-by-step during ageing in order to quantify its chemical and structural evolution.
The differences in mass variation between the different ageing modes (with or without sweat; with or without stabilizers) provided information on the hydrolytic action of the water. The chemical tranformations in the neighbourhood of the irradiated or immersed surfaces were studied by IR-ATR spectrometry in order to characterize the photo-oxidation and hydrolytic effects, as well as their coupling. The morphological modifications of the polymer were recorded by differential scanning calorimetry showing the evolution of the melting temperatures, the glass transition temperatures and the melting enthalpies.
Intercalated phyllosilicates; precursors for polymer-clay nanocomposites
M. Pospíšila, P. Čapkováa, Z. Weissb, M. Chmielováb, A. Kalendovác, J. Šimoníkc
aDepartment of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University Prague, Ke Karlovu 3, CZ-12116 Praha 2, Czech Republic
bCentral Analytical Laboratory, Technical University Ostrava, CZ-70833 Ostrava, Czech Republic
cTomas Bata University, Faculty of Technology Zlín, Náměstí T.G.Masaryka 275, CZ-76272 Zlín, Czech Republic
Clay minerals intercalated with organic species (long aliphatic chains, oligomers, polymers) are of great technological interest because of their applications as precursors for polymer-clay nanocomposites. Intercalation of clay minerals can be achieved by two different ways: (1) Ion-exchange reaction (exchange of interlayer cations by organoammonium cations) and (2) Adsorption of polar organic molecules into the interlayer space, based on ion-dipole interactions of guest species with interlayer cations and host layers.
In present work we investigate the structure of montmorillonite intercalated with cetyltrimethylammonium and cetylpyridinium cations and montmorillonite intercalated with neutral molecules of octadecylamine using molecular mechanics and molecular dynamics simulations combined with X-ray powder diffraction. Molecular simulations were carried out in a Cerius2 modeling environment.
Results of the structure analysis showed that cetylpyridinium and cetyltrimethylammonium cations are disordered in the interlayer space with the polar head-groups adjacent to the host layers. On the other hand the octadecylamine exhibits certain degree of order in the interlayer space in dependence on the guest concentration. For the low guest concentrations of octadecylamine we get the disordered interlayer structure. With higher concentration the monolayer arrangement of guests exhibits the smectic structure and with increasing concentrations the arrangements of guests becomes gradually bilayer. In addition to the detailed structure model including the characterization of disorder, we obtained the charge distribution and the energy characteristics such as total sublimation energy, partial host-guest and guest-guest interaction energies, exfoliation energy and their Van der Waals and Coulomb components.
A COMPARATIVE STUDY OF THE RHEOLOGICAL AND STRUCTURAL PROPERTIES OF GELATINS GELS OF MAMMALIAN AND FISH ORIGINS
A. Simon, Y. Grohens, L. Vandanjon, P. Bourseau, G. Levesque
Université de Bretagne Sud, Laboratoire Polymères & Procédés, Rue Saint-Maudé, BP 92116, 56321 Lorient Cedex, France
Gelatin is a
major industrial protein, especially in the food and
pharmaceutical fields, that is obtained by the thermal breaking
of collagen. Its uniqueness lies in the ability to form physical
thermo-reversible gels upon cooling. The accurate gelation
mechanism of gelatin is not yet fully understood. However, it is
well accepted that gelation results of a conformational
transition of gelatin molecules from random coils to
collagen-like triple-helical structures which joins several
chains together. As renaturation processed, a three-dimentional
network is formed.
From a long time, the traditionnal source of collagen has been mammals wastes, mainly bovine and porcine skins and bones. Since the recent ESB crisis, there is a growing interest in finding alternative raw materials of different origin. Among others, gelatin that can be isolated from fish collagen rich skins has a great potential as substitute to mammalian source.
This study undertakes a comparative analysis of the viscoelastic behaviour and the structural properties of gelatin gels from both mammalian and fish origins. The comparison is made between a gelatin derived from tuna skins and a traditional food grade pork gelatin. The viscoelastic behaviour of the gelatin gels was evaluated using a controlled-strain rheometer (HAAKE Rheostress-1).
The rheological behaviour of the gels were related to structural characteristics. In particular, the helical structures content of the different systems was determined through their specific optical rotation measured by spectropolarimetry. Both gelatins were also compared considering their amino-acid composition and molecular weight distribution.