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STRUCTURE OF PLURONICS - BASED NETWORKS
I. KRAKOVSKÝa, M. ILAVSKÝa,b, H. POSPÍŠILb, J. PLEŠTILb
a Department of Macromolecular Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
b Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovský Sq. 2, 162 06 Praha 6, Czech Republic
Pluronics are block ABA copolymers of poly(oxyethylene) (POE) and poly(oxypropylene) (POP). In contrast to POE, which is hydrophilic in a wide temperature range, interaction of POP with water is strongly temperature-dependent (POP is hydrophilic at temperatures close to 0 oC). Consequently, Pluronics are amphiphilic systems whose interaction with water can be controlled by their composition and temperature [1]. Various microphase-separated morphologies have been observed in Pluronic solutions in water [2].
As Pluronic chains are terminated by hydroxy groups, they can be end-linked, e.g., by the reaction with 4,4’-diphenylmethane diisocyanate (MDI) and poly(oxypropylene)triol (POPT) giving rise to a polyurethane network. The aim of this study is to get information about the influence of the end-linking on the structure and physical properties of the corresponding Pluronic networks obtained.
The systems studied were prepared by the reaction of pluronics L61, L64 and F68, differing in length of POE end blocks, with MDI and triols (trimethylolpropane and two poly(oxypropylene)triols, ARCOL 1030 and ARCOL 1042) at a constant initial stoichiometric molar ratio of reactive groups of [OH]PLU:[NCO]MDI:[OH]TRIOL=1:2:1.
Though Pluronics L61 and L64 seem to be homogeneous in dry state, microphase separation in corresponding networks has been revealed by small-angle X-ray scattering. In dry Pluronic F68 and the corresponding network, crystallinity has been detected by wide-angle X-ray scattering and differential scanning calorimetry. Formation of micellar structures in Pluronic aqueous solutions and gels has been observed by small-angle neutron scattering.
Support of this research by the Grant Agency of the Czech Republic (grant 203/00/1317) is gratefully acknowledged.
[1] J.K. Armstrong, et al.: J.Phys.Chem. 97, 3904 (1993)
[2] K. Mortensen : J.Phys.: Condens.Matter. 8, 103 (1996)
DYNAMIC CLUSTERING OF CELLULOSE TRIACETATE IN SOLUTION AS MEASURED BY DYNAMIC LIGHT SCATTERING
YOSHISUKE TSUNASHIMA
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, JAPAN
E-mail: tunasima@molmat.kuicr.kyoto-u.ac.jp
The solution dynamics of cellulose triacetate (CTA, the degree of substitution (DS) = 2.75) in methyl acetate was investigated by dynamic light scattering in the dilute-semidilute region at 10 – 30 ° C. CTA took four modes of motions. They were all diffusion motions because each decay rate was proportional to the square of the scattering vector q2. The fast mode was the translational diffusion of single CTA chain. The other three slower modes were the cooperative diffusions, or the dynamic structures, induced locally and temporarily in solution due to concentration fluctuations, and each correlation length was 3, 10, and 15-25 times larger than the size of a single chain. The clustering by concentration fluctuations would be originated from the intermolecular hydrogen bonds (HB) between C-6 position hydroxyls in CTA chains because the hydroxyls exist predominantly at the C-6 position, not at C-2 and 3 positions, in the anhydroglucose unit of CTA. Moreover, the structure and its stability depend strongly on solvents, the solvent mediating the HB formation in response to the change of environment with solution concentration, temperature, polarity, external forces, etc.
The single chain showed low temperature solubility, i.e., the hydrodynamic radius of single CTA chain RH (= kBT/6p h 0D0) increased with decreasing temperature. Here D0 is the translational diffusion coefficient. On the other hand, the correlation lengths of dynamic structures x , defined by the cooperative diffusion coefficient Dcoop as x = kBT/6p h 0Dcoop, increased with decreasing temperature slightly for two smaller dynamic structures but drastically for the largest one. The stability of structures were judged by estimating the dynamic second virial coefficient kD. It was positive for single chains with little temperature effect, i.e., single chains were in good solvent state. Whereas, kD was negative for three clusters in the range of c/c* = 0.321 – 1.37, showing poor solvent nature. ÷ kD÷ for the dynamic structures, however, decreased with increasing T for two smaller structures and exhibited a tendency to approaching zero, while ÷ kD÷ for the largest structure increased sharply around 30° C. This behavior would indicate that two smaller structures are unstable but the largest one is stable and tends to coagulate at higher temperature. The instability was enhanced at higher concentrations for smaller structures; the smaller structures might shift into the largest one with increasing concentration. These trends with T and c could be influenced strongly by HB, hydrophobic interactions (HPh), and solvent polarity. HPh would work between dispersed single chains. On the other hands, the HB plays the role in clustering as described above. Both interactions of HPh and HB might compete with each other for optimum realizable structures in given solution conditions.
DYNAMICS OF PENTABLOCKS IN SELECTIVE SOLVENTS
Č.KOŇÁKa, M. HELMSTEDTb, R. BANSILc
aInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic
bFakultät für Physik und Geowissenschaften, Universität Leipzig, Linnéstrasse 5, D-04103 Leipzig, Germany
cCenter for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215, U.S.A.
Dynamic properties of dilute and semidilute solutions of a pentablock copolymer, poly(styrene-block-butadiene-block-styrene-block-butadiene-block-styrene) (13000: 32000:9000:32000:1300) (Kaučuk Kralupy) obtained by the dynamic light scattering spectroscopy (DLSS) in a selective solvent for polystyrene, 1,4-dioxane, and for polybutadiene, n-heptane, are reported. The molecular weight was Mw = 1.2 x 105, polydispersity Mw/Mn = 1.10 and weight fraction of styrene was 0.35.
The dynamic mode in 1,4-dioxane solutions observed at concentration c £ 1 wt. % corresponds to the diffusion of block copolymer molecules. Formation of micelles was not observed. At 2 £ c £ 11 wt. %, two diffusive modes can be distinguished. The slow mode can be related to the diffusion of polydisperse animal-like clusters formed by the random association of pentablocks while the fast mode represents the cooperative (collective) diffusion of the copolymer matrix.
The pentablock copolymer is not soluble in n-heptane at room temperature but it is soluble at temperatures higher than 59 oC (cloud point). No flower-like micelles were observed above the cloud point. The samples prepared with c = 2, 4, 6 wt. % were turbid while the samples with c = 8 and 9 % were optically transparent. Three dynamic processes were extracted from DLS measurements of the samples with c = 8 and 9 %. The fast and slow mode was diffusive and the middle mode was relaxational. The fast diffusive mode can be related to the cooperative diffusion. The relaxation mode is probably due to the local dynamics of insoluble domains trapped in the network of the ordered physical gel. The slow dynamics is associated with heterogeneities in the physical gel, called microsyneresis and their dynamics.
Acknowledgments: Č.K. acknowledges financial support of the Grant Agency of the Academy of Sciences (A4050902), of the Grant Agency of the Czech Republic (203/99/0573) and of the Alexander von Humboldt Foundation. R.B. acknowledges support of the NSF Division of Materials Research (9618467). M.H. thanks the Deutsche Forschungsgemeinschaft (SFB 294) for financial support.
Dynamic Light Scattering of Polymer Networks of N-isopropylacrylamide Gels Prepared under High Pressure
Tadayoshi KITADA and Norihide FUJIKAWA
Department of Applied Physics, Faculty of Engineering, Osaka City University, Sugimoto 3, Sumiyoshi-Ku, Osaka 558-8585, Japan
Dynamics of the network of poly (N-isopropylacrylamide) gels (NIPA gel) prepared under the high pressure is studied with dynamic light scattering measurement (DLS). The shrinking speed in the volume phase transition of the NIPA gel was very fast in comparison with that of a conventional NIPA gel. The deswelling time of the gel rod of 2.2mm in diameter prepared at 193MPa was about 200s.1) The NIPA gels have been prepared at 20˚C with a conventional method,2) except under pressure in the range of 200MPa. The concentrations of the NIPA-monomer and the crosslinker, N, N’-methylenebisacrylamide, were 695mM and 8.36mM, respectively.
We report the results of the preparation-pressure dependence of collective diffusion coefficient DC, ensemble-averaged scattering intensity <I>E, and fluctuated intensity <IF>T of the networks of those gels in the ”reference” state after the gelation, the state after pressure release, and as well as the swollen state.
The preparation pressure dependence of DC at 20°C is shown in Fig. 1. The DC’s correspond to the reference state (solid circle), the state after pressure release (square), and the swollen one (empty circle), respectively. DC of the networks in the reference state only has two components. The one is a similar increasing function of preparation pressure to that after pressure release, and the other a decreasing function, tending to go to zero near the critical pressure of 182MPa. DC of the swollen networks has a critical point near 223MPa.
Fig.1 Preparation pressure dependence of collective
diffusion coefficient at each state of NIPA gels
Light scattering measurements of the hyaluronate alkyl derivatives
Karolina Benešová1, Lubomír Lapčík, Jr.2, Lubomír Lapčík2, Dieter Lath3
1 Institute of Physical and Applied Chemistry, Faculty of Chemistry, Brno University of Technology, Purkyňova 118, 612 00 Brno
2 Institute of Physics and Material Engineering, Faculty of Technology, Tomas Bata University in Zlín, nám. TGM 275, 762 72 Zlín
3 Polymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 842 36 Bratislava
Results of the static light scattering measurements of different alkyl substituted hylauronate derivatives in 0.1 M saline solutions are discussed. From measured Zimm plots basic macromolecular characteristics were determined, namely radius of gyration, weight average molecular weight and second virial coefficient for each derivative. There was found expanded coil contraction due to the effective intra–molecular hydrophobic association. The latter data were correlated with the viscometric measurements and the parameters of Mark–Houwink equation were calculated.
Time-resolved synchrotron x-ray diffraction studies on imidization-induced structural evolution in poly(3,4'-oxydiphenylene pyromellitamic acid)
T. J. Shin, B. Lee, J.W. Lee, and M. Ree*
Dept. of Chemistry, Center for Integrated Molecular Systems, BK21 Functional Polymer Thin Film Group, and Polymer Research Institute, Pohang University of Science & Technology, San 31, Hyoja-dong, Nam-gu, Pohang 790-784 South Korea
(Tel) +82-54-279-8143 (Fax) +82-54-279-3399
(E-Mail) stj@postech.ac.kr
The thermal imidization of poly(3,4'-oxydiphenylene pyromellitamic acid) precursor in film, which was cast from its solution in N-methyl-2-pyrrolidone (NMP), was investigated in detail by time-resolved wide-angle x-ray diffraction, FT-IR spectroscopy, and thermogravimetry. The precursor revealed only a short-range order converts to the corresponding polyimide shown a nice crystalline structure. It is evident that the residual NMP strongly bound to the precursor plays an important role in the imidization. The decomplexation of NMP solvent from the precursor chains occurs prior to the onset of imidization. On the heating run with 2.0 K/min the imidization reaction takes place before the structural evolution begins. The maximum rate of imidization reveals at 166ˇĆC. The structural evolution starts at 136ˇĆC where the imidization of 3.3 % is made. Such imidization-induced structural evolution is done mainly up to only 166ˇĆC which provides only 45.5 % imidization. In contrast, the imidization is completed above 334ˇĆC. The overall crystallinity in the fully imidized polymer film is only 21.4 %. In addition, Bragg spacing and mean crystallite dimension of the ordered structure evolved are estimated as a function of temperature.
The structural analysis of PCL/PVB band spherulite by the simultaneous micro small and wide angle X-ray scattering method
Y. NOZUEa, S. HIRANOa, S.UENOb, A. IIDAc, T. NISHIa, Y. AMEMIYAa
aDepartment of Applied Physics, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan
bFaculty of Applied Biological Science, Hiroshima University, Higashi-Hiroshima 739-8528, Japan
cPhoton Factory, Institute of Materials Structure Science, High-Energy Accelerator Research Organization, Tsukuba 305-0801, Japan
The microbeam small and wide angle x-ray scattering (micro SAXS/WAXS) technique gives the novel information about micron-scale structural distribution (or inhomogeneity) of polymer crystal. By using micro SAXS/WAXS, we have studied the crystallization and melting behavior of miscible polymer blend PCL (poly-ε caprolactone)/PVB (poly-vinyl butyral) and the spatial distribution of its band structure. In PCL/PVB, the very large spherulite (~several mm in radius) with highly regular band structure is formed because of low frequency of nucleation. By irradiating an X-ray microbeam near the growth edge of the spherulite, we have measured the lamella formation at the growth front. It is found that a PCL/PVB crystal has a broad distribution of lamella repeating length (150~180Ǻ ) and the longer periodic structure grows before the appearance of the shorter period. We have also scanned the X-ray microbeam along the radial direction of the band spherulite and have observed a periodic change of scattering pattern by simultaneous micro SAXS/WAXS measurement (FIG.1 (A), (B)). The interpretation of the results will be discussed.
FIG.1 (A) FIG.1 (B)
Dynamics of Probe Particles on a Complex systém
G. Fadda1, D. Lairez1, J. Pelta2
1 - Laboratoire Léon Brillouin, CEA/Saclay, France
2 - Département de Biologie, Université de Cergy Pontoise, France
The use of spherical probe particles to investigate the viscoelastic properties of polymer solutions have been already considered . In semi-dilute solution, it has been shown that for R/x>1 (R is the particle size and x the correlation length of concentration fluctuations) the dynamics of the particles studied by quasi elastic light scattering is sensible to the macroscopic properties of the solution. It has been already reported that these measurements are sensitive to the sol gel transition. We propose, here, a detailed interpretation of these measurements performed at qR=1 and qx<1 during gelation.
We show that focusing on the short-time and long-time behavior of the autocorrelation function, it is possible to simply interpret our data in terms of the divergence of the viscosity and emergence of a shear elastic modulus near the gel point. With our crude analysis we were able to grasp the critical behavior of gelation and to obtain the two critical exponents of the transport properties.
THE EFFECT OF INITIAL MATRIX MATERIAL ON THE STRUCTURE OF RADIATION GRAFTED ION-EXCHANGE MEMBRANES:WAXS AND SAXS STUDIES
K. JOKELAa, R. SERIMAAa, M. TORKKELIa, N. WALSBYb, F. SUNDHOLMb, T. KALLIOc, G. SUNDHOLMc
aDepartment of Physics, P.O.Box 64, FIN-00014 University of Helsinki, Finland
bDepartment of Chemistry, P.O.Box 55, FIN-00014 University of Helsinki, Finland
cLaboratory of Physical Chemistry and Electrochemistry, P.O.Box 6100, FIN-02015 Helsinki University of Technology, Finland
This study is concentrated on the structure studies of styrene grafted and sulfonated poly(vinylidene fluoride), PSSA-g-PVDF, membranes. These membranes have been developed to offer a new, inexpensive raw material for fuel cell applications. The structure of PSSA-g-PVDF membranes is a very complicated combination of partly crystalline PVDF, grafted in the amorphous regions with sulfonated polystyrene chains1-3. Wide angle x-ray scattering, WAXS, studies have shown how radiation, grafting, crosslinking and sulfonation affect the structure and proton conductivity of the membranes1. According the small angle x-ray scattering, SAXS, and anomalous SAXS, ASAXS, measurements the macrostructure of membranes forms lamellae and ionic clusters. The structure of ionic cluster can be described by using the Yarusso liquid-like hard sphere model or paracrystalline model2,3.
One method to vary properties of membranes is to use different matrix materials. E.g. porous and non-porous PVDF and poly(vinylidene-co-hexafluoropropylene), Kynar, have been used as a matrix1-3. In this study the structural differences between different matrix materials have been studied. The crystallinity of different PVDF-based matrix materials has been determinated using the known crystal structure of PVDF and the intensity curve of amorphous PVDF. The intensity curve of amorphous PVDF has been calculated on the basis of molecular modeling. SAXS studies have been made to get information about lamellar period and the ionic aggregates. Some of the membranes have been also measured after fuel cell tests and clear changes on the structures can be detected.
[1] S. Hietala, S. Holmberg, M. Karjalainen, J. Näsman, M. Paronen, R. Serimaa, F. Sundholm and S. Vahvaselkä, J. Mater. Chem., 7(5) (1997), 721
[2] M. Torkkeli, R. Serimaa, V. Eteläniemi, M. Toivola, K. Jokela, M. Paronen, F. Sundholm, J. Polym. Sci., Part B, 38 (2000), 1734
[3] K. Jokela, R. Serimaa, M. Torkkeli, M. Elomaa, F. Sundholm, N. Walsby, T. Kallio and G. Sundholm, J. Appl. Cryst., 33, (2000), 723
Supermolecular AND MICROFIBRILLAR Structure of polypropylene / elastomer BLEND FIBRES
M. LINEKa, J. FABIAa, A. TARNIOWYb
a Textile Institute,Technical University of Łódź, Branch in Bielsko-Biała, Willowa 2, PL-43-309 Bielsko-Biała, Poland
bResearch and Developement Institute of Rubber and Vinyl Plastics, Oświęcim, Poland
Modification of polypropylene (PP) fibres, using different additives affected their mechanical properties, is well-known.
The aim of this research is to present some results of modification of PP filament by two different elastomer additives: dynaron – statistical stryrene-butadiene block copolymer, and butadiene-acrylonitryl rubber powder. Typical behaviour of these blends is mutual penetration of continious phases of each components.
The parameters of a new supermolecular structure of modified PP filament based on the structural investigations using modern analytical methods such as: wide angle X-ray scattering (WAXS), small angle X-ray scattering (SAXS), differential scanning calorymetry (DSC) an other, have been calculated. Above parameters have allowed to construct a general model of structure and to describe its transformation in dependence on content of the modifying additive and also on conditions of the fibre forming process. Determination of the content of a crystalline phase in polymers by the x-ray methods requires the separation of an experimental diffraction pattern into two components connected with the scattering from crystalline and amorphous regions, respectively. For this purpose the method elaborated by Hindeleh and Johnson was used. The degree of crystallinity was calculated as the ratio of the total area under the resolved crystalline peaks to the total area under the unresolved X-ray scattering curve. The mean crystallite sizes were estimated by means of the familiar Scherrer equation.
Microstructure of blend fibres was described by modified Takayanagi’s model, verified by means of electron scanning microscopy and investigations of chosen mechanical properties.
Time-resolved light scattering in polymer blends: Phase dissolution
J. Holoubek
Institute of Macromolecular Chemistry
Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic
Time-resolved light scattering measurements and image analysis have been conducted to investigate the influence of diblock copolymers on the kinetics of phase separation and dissolution of polymer blends. The blends studied were those of polystyrene and poly(methyl methacrylate) (PS/PMMA) with or without diblock copolymers composed of the corresponding homopolymer blocks. The time evolution of the cocontinous structure in polystyrene-PMMA blends has been studied during an annealing process. The spinodal peak position, qm(t,T), (where qm is the wavenumber of the periodicity in the cocontinuous structure) and the corresponding intensity Im(t,T) have been compared with theoretically predicted values of exponents for distinct time scales of the phase dissolution in various temperature regimes. The prevailing effect of phase dissolution for the PS/PMMA/PS-b-PMMA system in the studied temperature regimes is the growing size of separated domains. A non-exponential decrease in I(qm) is observed in the initial time period. Statistical properties of speckled intensity patterns from phase-dissolving blends are investigated.
The influence of diblock copolymers on the kinetics of phase separation and dissolution of polymer blends with a cocontinuous structure has been studied.
Acknowledgement
Support of the Grant Agency of the Academy of Sciences of the Czech Republic and Grant Agency of the Czech Republic (grant No. 203/99/0573) is gratefully acknowledged (grant No. A4050902).
M.T. Tarrazo, M.C. Blanco, D. Leisner, M.A. López-Quintela
Dynamic Light Scattering Study of Percolation in Microemulsions
Available in
printed programme booklet only.
F. Cuppo, S. Paoletti, H. Reynaers
Aggregation of κ-Carrageenan
Induced by Cesium Cations – Light Scattering Study
Abstract not supplied
E. Theunissen, A. Antoun, R. Jerome, K. Mortenesen, H.
Reynaers
Reinforced Triblock Copolymer Gels. A Structural Study
Abstract not supplied
SAXS, WAXS and DSC Study of sPS/aPS Blends
J. Baldrian1, A. Sikora1, Z. Kruliš1, Z. Horák1, D. Konečný2, A. Pleska2, V. Varga2, P. Šindelář3
1Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague, Czech Republic, baldrian@imc.cas.cz
2Synthetic Rubber Research Institute, Kaučuk a.s., Kralupy nad Vltavou, Czech Republic
3Polymer Institute, Brno, Czech Republic
Since syndiotactic polystyrene (sPS) with very high degree of stereospecificity (>96 %) was synthetized1, it has attracted considerable interest mainly owing to its properties, which are interesting for technical applications. Polymer blends give an effective way of developing new materials with tailored properties. An interesting chance in this field is blending of sPS with atactic polystyrene (aPS). The aim of this work was to study structure development of sPS in blends with aPS during annealing.
Blends were prepared by melt-blending and were studied during gradual annealing in the temperature interval 105 – 180 ° C using of SAXS, WAXS and DSC methods. WAXS results have shown that sPS in blends crystallizes similarly to neat sPS in distorted a ' modification. The crystallinity of sPS is strongly influenced by the presence of aPS. Its values are lower than it would correspond to the crystallinity of neat sPS prepared under identical conditions. This indicates partial miscibility of components.
SAXS curves of crystalline sPS and sPS/aPS blends do not reveal low-angle peaks indicating lamellar crystallinity. The scattering effect was ascribed to "finely divided voids on grain boundary phase"2. The SAXS curves are of the same shape as in the case of amorphous samples. A small electron density difference of amorphous and crystalline sPS, which follows from the published data, supresses development of SAXS peaks. The swelling of samples in decalin increased this difference and visualized the lamellar periodicity of crystalline sPS. It follows from a comparison of SAXS curves of dry and swollen samples that no voids are present in the structure.
1 Ishihara N., Seimiya T., Kuramoto M., Uoi M., Macromolecules 1986, 19, 2464
2 Barnes J. D., McKenna G.B.: Polym.Eng.Sci. 1997, 37, 1480
Research was supported by the Grant Agency of the Czech Republic (grant No:106/99/0557) and Grant Agency of the Academy of Sciences of the Czech Republic (grant No:A4050007).
VARIETY OF MESOPHASES FORMED BY POLYMETHACRYLATES WITH HIGHLY TAPERED SIDE CHAINS AND THEIR MACROMONOMERS
S.N. CHVALUN*, M.A. SHCHERBINA*, I.V. BYKOVA*, J. BLACKWELL**, V. PERCEC***
*Karpov Institute of Physical Chemistry, Vorontsovo pole, 10, Moscow, Russia. 103064. sherbina@cc.nifhi.ac.ru
**Case Western Reserve University, Cleveland, OH 44106-7202 USA.
***University of Pennsylvania, Philadelphia, PA 19104-6323
The various mesophases built up from polymethacrylate with highly tapered side groups and from its macromonomers are discussed.
It turns out that at room temperature the samples studied form the ordered columnar hexagonal phase 0h in which the molecules self-assemble in the cylindrical pine-tree helical structures with the diameter of about 40-60 Å and 81 helical symmetry. There is no register between adjacent columns packed in two-dimensional hexagonal lattice. Heating of the samples studied is accompanied by two phase transitions usually. The first order-disorder transition corresponds to the internal disordering of columns and to the transition to disordered columnar hexagonal phase h, while the second transition is the isotropisation. The order-disorder transition is cooperative process of consecutive ”melting” of alkyl tails and mesogen groups and it is accompanied by abrupt change in d-spacing of hexagonal lattice. The further heating of disordered columnar phase results in the significant decrease of column diameter with the negative coefficient of thermal expansion about -(1¸ 2)· 10-3 К-1, probably due to unwinding of chain helices inside the columns at temperature increasing. The stability of columnar phase in polymethcrylate with a highly tapered side groups and on its monomer precursors is determined by the interaction between mesomorphic aromatic groups and aliphatic matrix where the disordered columns are embedded.
Metastable two-dimensional phase of lower symmetry
(monoclinic) can be observed as well. The fluorination of the
alkyl tails enhances of their self-assembly ability and lead to
the formation of the cubic bicontinuos Ia
d gyroid phase under the complex
combination of thermal and stress effect at the temperatures near
the order-disorder transition (85°
C).
This work was supported by Russian Foundation for Basic Research. Grant No 00-03-33125 (at Karpov Institute)
MODIFICATION OF THE STRUCTURE AND PROPERTIES OF POLYETHYLENE OF DIFFERENT MOLECULAR WEIGHTS AND MORPHOLOGY BY GAMMA-IRRADIATION
M.A. SHCHERBINA, A.V. CHERNYKH, V.I. SELIKHOVA, V.S. TIKHOMIROV, S.N. CHVALUN
Karpov Institute of Physical Chemistry, Vorontsovo pole, 10, Moscow, Russia. 103064. sherbina@cc.nifhi.ac.ru
The effect of g - irradiation (D=0 – 5 MGy in vacuum) on mechanical and thermal characteristics and structure of linear PE of different molecular weights (3x104, 3x105, 106) and morphology (isotropic bulk and highly oriented samples, single crystal mats and ultra-high drawn to ratio 200 films of high molecular weight PE) was studied.
It was shown that, as a result of irradiation, the Young modulus of oriented bulk samples of medium and high MW increases, while the modulus of LMWPE decreases. As suggested it is due to the different contributions of the processes of cross-linking and destruction of tie molecules in the samples of various molecular weights. Structural investigations showed some changes in crystalline phase of all the samples studied; however, these changes were almost identical in polymers of different molecular weights. The most remarkable differences were observed in the behavior of amorphous regions of low- and high-molecular weight PE with irradiation. SAXS method detected the significant increase both in the average amorphous density and in the density of intrafibrillar amorphous regions, the most profound in PE of medium and high molecular weights, pointing to the prevailing role of crosslinking in these samples. Based on the data obtained the localization of molecular cross-linking and destruction processes in isotropic and oriented samples of PE of different molecular weights was established.
Comparative study of thermal behavior of irradiated samples in bulk and solvents revealed the peculiar properties of sol and gel fractions and their contributions to the total fusion heat
This work was supported by Russian Foundation for Basic Research. Grant No. 99 – 03 – 33422 (at Karpov Institute)
CRYSTAL STRUCTURE AND PROPERTIES OF THERMOELASTOPLASTICS, BASED ON ALPHA-OLEFINS AND CARBON MONOXIDE CO- AND TERPOLYMERS
D.V. ANOKHIN*, V.M. NEVEROV*, S.N. CHVALUN*, B. RIEGER**, F. HOLLMANN**
*Karpov Institute of Physical Chemistry, Vorontsovo pole, 10, Moscow, 103064, Russia.
** Universitat Ulm, Abt. Anorganische Chemie II, Materialien und Katalyse D-89069, Ulm, Germany
anohin@cc.nifhi.ac.ru
Perfectly alternative polyketones are of considerable interest from both academic and industrial standpoints, because of low cost, the potential use as a precursor for new classes of polymers, high adhesion to inorganic material, possible photo-and biodegradability, etc. The recent catalyst developments make available synthesis of polyketones with highly defined molecular weight, stereo- and regioregularity.
Propylene-carbon monoxide copolymer and terpolymers of propylene-CO and ethylene-CO with content of ethylene-CO less than 40% synthesized by the method with preliminary set of monomer concentrations (Pre-Set) reveal an excellent elastic properties while terpolymers with >60% of ethylene-CO are typical thermoplastics. DSC data and X-ray analysis reveal a highly blocky microstructure of the terpolymers, obviously due to the difference in reactivity of ethylene, CO and propylene units. It was determined that ethylene-CO blocks crystallize in distorted b -modification and propylene-CO chains forms triclinic unit cell (a=b=9.49Å, c=9.0Å, a =b =109.87° , g =108.04° ). Surprisingly, though the stereo- and regioregularity of polypropyleneketone were not controlled during the synthesis, the polymer chains crystallize in triclinic lattice containing two 31 helices forming stereocomplex of L- and D-enantiomers within the unit cell.
To avoid the long block formation and improve the elastic properties of the material the new synthesis technique based on a discontinuous addition of ethene to a running propene-CO polymerization (Pulse-feed) was developed. On X-ray patterns of the ”pulse-feed” synthesized terpolymers the traces of b -form of ethylene-CO are absent but in some of constrained drawn samples the new set of reflections in addition to propylene-CO stereocomplex is observed. These stress-induced reflections correspond to the distorted orthorhombic lattice of propylene-CO similar to the one observed in the pure isotactic l-polypropyleneketone (a=10.68Å, b=6.18Å, c=9.00Å) with two isomorphous helices passing through the unit cell.
This work is supported by INTAS (project №97-0418)
CHORD LENGTH DISTRIBUTIONS A(l) AND SCATTERING PATTERNS I(h) OF INFINITELY LONG GEOMETRIC FIGURES
W. Gille
Department of Physics, Martin-Luther-University Halle-Wittenberg, SAS-Laboratory, Hoher Weg 8, D-06120 Halle, Germany
The geometric description of samples involving long stretched particles in the order of some nanometres is considered.
The intrinsic behaviour of the chord length distribution (c.l.d.) A(r) and the small-angle scattering intensity I(h) are discussed for plane stripes, quadratic rods, rectangular rods, elliptic needles, circular rods, hollow cylinders, hemicircular rods and triangular rods. For infinitely long figures there does not exist a Tayler-series expansion of the scattering intensity
I(h) in the origin h=0. Further, the second moment of A(r) does not exist. Otherwise, the asymptotic scattering behaviour for large scattering vectors h is clearly defined, depending on the specific shape parameters of the body considered. It is advantegeous to analyze this by use of so-called normalised Porod-plots P1(h). Here, a special normalization strategy is developed. Based on an experimental relative measurement I(h), a function P1(h) can be obtained. P1(h) is connected with A(r). P1(h) curves possess a more or less specific oscillating behaviour around the normalized Porod asymptote P1(h)=1. Here, depending on the arrangement of the interfaces
of the geometric figure, two basic situations exist:
There exists an intimate connection between the theory of chord length distributions and the small-angle scattering experiment, see for example (Hsin-I. Wu, P.W. Schmidt, Intersect distributions and small-angle X-ray scattering theory, J. Appl. Cryst. 6(1973)66-75, or W. Gille, Chord length distributions and small-angle scattering, The European Physical Journal B, 17(2000)371-383), or W. Gille, The SAS structure functions of two infinitely long parallel circular cylinders, Comp. Mater. Sci. 20(2001)181-195). It is useful to scientists in the field of materials research applying scattering methods to go back to the first principles of the geometrical theory of c.l.d.'s.
I.P.Dolbnya, W. Bras
Time Resolved X-ray Scattering Experiments: Instrumentation
Issues
Not supplied
BICONTINIOUS STRUCTURES IN SOME POLYMER SYSTEMS WITH CUBIC MESOPHASES
S.N.CHVALUN, A.N.YAKUNIN*
Laboratory of Polymer Structure, Karpov Institute of Physical Chemistry, Vorontsovo Pole, 10, Moscow 103064, Russian Federation, yakunin@cc.nifhi.ac.ru
Using self-assembly and self-organizing processes of supramolecular nanostructures at creation of new polymeric materials sensitive to various external influences such as changes of temperature, pressure, electrical or magnetic field, chemical nature of an environment etc., is one of the major directions of modern science. The molecular recognition of biopolymer fragments, their ordering and the self-assembly of consisting elements result in a spontaneous formation of functional supramolecular structures owing to weak non covalent interactions such as van der Waals and electrostatic forces, hydrogen bonding, hydrophobic interactions. Frequently one can observe that the variety of the forms of supramolecular objects is mainly defined by shapes of elementary units.
However, the form of a self-organizing supramolecular structure and lattice types depend not only on chemical nature but also on external conditions.
The aim of the present study is to analyze the 3D structure of polymer colloid complexes composed from network polyelectrolytes and oppositely charged surfactants by experimental, theoretical and computer simulation methods and to discuss a possibility of the formation of bicontinuous structures in systems of cubic symmetry.
Using a simple hypothesis not only designs the model by means of that the theoretical scattering curve is obtained, but also allows to catch more fine details owing to which it becomes possible to interpret the experimental results from a view of the formation of the bicontinuous structure: for sections by planes z = 0.25, 0.75 in the regions near to points (0.25, 0.25), (0.25, 0.75), (0.75, 0.25), (0.75, 0.75) the electronic density is increased, i. e. there are ionic clusters at the points. Secondly, the geometric characteristics of the complexes can be easily estimated by help of the present model. Finally, the combination of the theoretic and experimental methods together with computer simulations is the base which enables to obtain the unique results.
The authors are thankful to Russian Foundation of Basic Research (Grants No 00-03-33125 and 01-03-32225) for financial support.
Microheterogeneities in aqueous solutions studied by small-angle neutron scattering
L. Almásya, L. Csera, G. Jancsób
aResearch Institute for Solid State Physics and Optics, Budapest-1525 POB 49, Hungary
bAtomic Energy Research Institute, Budapest-1525, POB 49, Hungary
Aqueous solutions of many simple organic liquids exhibit strong deviations from the ideal mixture behavior. This 'non-ideal' mixing is thought to have its origin in the balance between the entropic and enthalpic parts of the free energy function, caused by the strongly oriented hydrogen bond network. The non-monotonous dependence of the thermodynamic quantities on the concentration are accompanied by structural features, which can be described in terms of long-range concentration fluctuations, and can be measured by small-angle scattering techniques.
In the present work we demonstrate the applicability of SANS to obtain quantitative characteristics of preferential ordering of the two components using the Kirkwood-Buff theory of solutions.
Aqueous solutions of 3-methyl pyridine studied by DLS
L. Almásya,b, D. Lairezb
aResearch Institute for Solid State Physics and Optics, Budapest-1525 POB 49, Hungary
bLabratoire Léon Brillouin, Saclay, Gif-sur-Yvette 91191 CEDEX , France
Static and dynamic light scattering measurements have been performed on mixtures of heavy water and 3-methyl pyridine of different concentrations at room temperature. Most of the DLS spectra exhibit a single exponential relaxation mode, characteristic for diffusive motion of a particle in viscous medium. At some concentrations further relaxation components were visible, with amplitudes ten times smaller and relaxation times fifty times larger than those of the main component. Analysing the short-time parts of the spectra the characteristic sizes of the scattering (moving) objects could be calculated from the diffusion coefficients using the Stokes-Einstein relation. The obtained sizes correspond to the average dimensions of methyl pyridine - water clusters observed by small-angle neutron scattering.
Fig. 1. Characteristic sizes calculated from the measured diffusion coefficients
Fig. 2. DLS spectra of one sample
QENS studies of water - picoline mixtures
L. Almásya,b, M.-C. Bellissent-Funelb, L. Csera, G. Jancsóc, J. M. Zanottib
aResearch Institute for Solid State Physics and Optics, Budapest-1525 POB 49, Hungary
bLabratoire Léon Brillouin, Saclay, Gif-sur-Yvette 91191 CEDEX , France
cAtomic Energy Research Institute, Budapest-1525, POB 49, Hungary
We have studied mobility of the solute and the solvent in aqueous solutions of 3-methyl pyridine. This system has a closed-loop immiscibility region between 37 and 114 oC at normal pressure, if heavy water is used as solvent, and it is fully miscible with light water at any concentrations and temperatures. In the present study the origin of the partial miscibility behavior is sought through microscopic dynamical features of the solute-solvent interaction.
Time-of-flight quasi-elastic neutron scattering measurements have been performed on the MIBEMOL spectrometer at the LLB, Saclay. Three concentrations of 3MP-water mixtures were prepared using both protonated and deuterated solute and solvent, in order to separate the contribution of hydrogen atoms of the different species. The analysis of the translational diffusive motion at different concentrations shows that at high concentration (25 mol% picoline) the diffusion coefficient of water strongly decreases and becomes similar to that of the solute, indicating strong coupling in the motion of the solute and the solvent.
WAXS AND SAXS INVESTIGATIONS OF THE SUPERMOLECULAR STRUCTURE OF POLYPROPYLENE POY FIBRES MODIFIED
WITH ELASTOMERS
CZ. ŚLUSARCZYKa, A. WŁOCHOWICZa, J. FABIAa, H. STRUSZCZYKb
aTextile Institute, Technical University of Łódź, Branch in Bielsko-Biała, Willowa 2, PL-43-309 Bielsko-Biała, Poland
bInstitute of Chemical Fibres, Łódź, Poland
Technology of production of polypropylene fibres with extensioned elasticity requires two modifications. The first relies on use of partially oriented yarn (POY) production method, through triple increase of speed of forming fibres. The second is the physical modification of PP material, based on blending with hydrogenated styrene-butadiene rubbers (HSBR) elastomer. In contrast to PP fibres obtained by classical technology, the supermolecular structure of PP POY filaments is created in different way.
The aim of presented studies is to characterize this structure by means of wide-angle (WAXS) and small-angle (SAXS) X-ray scattering methods and by scanning electron microscopy.
In WAXS investigations we developed a procedure for the quantitative evaluation of the degree of crystallinity in polymer blends. The procedure was elaborated for two-component polymer blends consist from a semicrystalline polymer (SC) and a completely amorphous one (A). The procedure is based on the assumption that the components are immiscible and scattered X-ray intensity contributions arising from crystalline and amorphous regions of a polymer blend can be separated. For this purpose we assumed that the shape of intensity contributions arising from the amorphous polymer A is not dependent on the components’ mass proportions. It means that the shape of polymer A intensity contributions in blends’ diffraction pattern is the same as for pure polymer A. Knowing mass proportions of components in considered blend and the diffraction pattern from pure amorphous component A, one can subtract the latter from the diffraction pattern of the blend and obtains the contribution arising from the second component i.e. the semicrystalline polymer SC. Than, the latter can be resolved into individual crystalline peaks and amorphous halo by means of peak-fit procedure. The crystallinity is calculated as the ratio of the integrated intensity under crystalline peaks to the integrated intensity under the whole X-ray diffraction trace.
In the paper the procedure was used to determine the influence both the content of elastomer and technological operations of dawing and texturing on the supermolecular structure of a new generation of PP POY fibres modified with HSBR elastomer. Results of WAXS investigations were supported by SAXS and SEM observations.
TIME RESOLVED SAXS/WAXD STUDIES OF LIQUID CRYSTALLINE OLIGOESTER-iPP BLENDS
Jarosław Janicki, Andrzej Wlochowicz
Technical University of Łódź, Branch in Bielsko-Biała, Willowa 2, 43-309 Poland
Termotropic liquid crystalline polymers usually contained rigid-rod chemical structures and therefore possessed unique properties such as low melt viscosity and high modulus. Blending such liquid crystalline polymers with semicrystalline polymer appeared to be very attractive because of advantages in lowering the viscosity during processing and in reinforcing the final mechanical properties of the polymer matrix. However, due to positive enthalpy of mixing rigid-rod polymer with flexible-chain of semicrystalline polymer, the miscibility was rarely found and knowledge of structure-property relations is still far from complete.
The aim of the reported paper was to investigate the nanostructure of thermotropic liquid crystalline oligoester and its blend with iPP, by means synchrotron SAXS/ WAXD and DSC methods. A liquid crystalline compounds having three rings rod–like mesogen and aliphatic end groups has been synthesised. The aromatic rings in the mesogen were bounded with ester groups while the aliphatic end–groups consisting of five carbon atoms were connected with aromatic ring by ester bounds. The synthesised liquid oligoester exhibit ability of thermotropic mesophase formation, confirmed by microscopic observation and DSC analysis. At about 118° C the melting point is observed and isotropization is at 152° C. Blends of iPP and olygoesters were prepared in the weight ratio of 80/20 from the melt by means laboratory extruder.
The SAXS and WAXD investigations were carried out by means synchrotron beamline on the X33 double focusing camera of the EMBL in Hasylab, on the storage ring DORIS III of the DESY in Hamburg at wavelength of 0.15 nm.
The diffraction WAXD patterns of olygoester consist of the strong crystalline peaks and relatively low amorphous halo indicates the well ordered structure. This is confirmed by SAXS investigations. SAXS curves exhibit a distinct diffraction maximum which angular position is connected with the supermolecular structure with different electron densities of phases separated by repeated distance. Values of the repeated distance were evaluated using Bragg’s law and they are 4.4 nm for solid crystal and 3.7 nm for liquid crystalline phase. Computer modelling of macromolecular chain gives the length equals 4.2 nm. This is in a good relation to the value of the repeated distance and indicates smecthic liquid crystal structure. SAXS patterns for the olygoester-iPP blend exhibit distinct diffraction maxima both for iPP and LCO. The supermolecular structure of the blend was characterized by the thickness of crystalline lamelae, values of long periods and degree of crystallinity. Based on obtained results, one can say that liquid crystalline olygoester is pertially miscible with isotactic polypropylene.
ANALYSIS OF SINGLE- AND MULTIPLE SCATTERING USING THE 3-D CROSS-CORRELATION TECHNIQUE
E. SEVENARD and W. SCHRÖER
Institut für Anorganische und Physikalische Chemie, Universität Bremen,
D 28359 Bremen, Germany, e-mail: schroer@chemie,uni-bremen.de
In highly turbid samples the presence of multiple scattering obscures the analysis of the intensity and of correlation functions obtained in the conventional light-scattering experiments. Cross-correlation techniques, enable to separate the contributions of singly from multiply scattered light by experimental means. Different methods have been proposed [1] and successfully applied [2,3]. The intensities and the time correlation functions for both, the singly and multiply scattered light, can be determined by analyzing the scattering intensity, the auto- and the cross-correlation function. The intensity correlation function of singly scattered light is given by the time dependence of the cross-correlation function. The amplitude of the cross-correlation function is determined by the ratio of the single-scattering intensity to the total scattering intensity, hence, fixes the complimentary ratio concerning the multiple scattering intensity.
We report experiments on solutions of Latex (126 nm, transmission 1-99 %) at different scattering angles (30°-150°) and at various positions in a square sample. The intensity-correlation functions of the multiply scattered light are determined as difference from the auto-correlation functions (corrected for the detector deficiencies as dead-times, after-pulsing and dark current [4]) and the cross-correlation function. The results are found to be in agreement with that obtained by fitting the auto-correlation function to two exponentials. The single-scattering correlation function is a single exponential with the characteristic angle dependence of the diffusional motion of the particles. The first cumulant of the multiple-scattering correlation function is independent of the scattering angle and of the position inside the sample but increases with the number density; it can be considered as given by the product of the average number of the scattering events along the light path and the averaged exponent of the single-scattering correlation function.
[1] K.Schätzel J.Mod.Opt. 38 1849 (1991).
[2] L.B.Aberle, P.Hülstede, S.Wiegand, W.Schröer, W.Staude Appl. Opt.37 6511 (1998).
[3] E.Overbeck and C. Sinn J.Mod. Optics 46 303 (1998)
[4] I. Flammer and J. Ricka Appl. Opt.36 7508 (1997)
M. Durell, J.E. MacDonald, R.A.L. Jones, R. Randel, H. Loebl,
P. Steadman
Surface X-Ray Diffraction in Thin PET Films
Abstract not supplied
Ternary polymer blends and their solutions: Synthesis of model systems and their dynamic properties
Peter Černoch, Lubomír Lochmann, Petr Štěpánek
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague, Czech Republic
We have investigated dynamic properties of ternary polymer blends in bulk and in solutions at compositions corresponding to the bicontinuous microemulsion phase. Two blends were studied: polystyrene / poly(methyl methacrylate) and poly(octylstyrene) / poly(butyl methacrylate). The polymers were prepared by anionic polymerization. The ternary blends always contain equal amounts of the two homopolymers, approximately 10 % of the diblock copolymer made of the same monomers and a variable amount of the solvent, toluene. We have used dynamic light scattering to obtain the distributions of relaxations times as a function of temperature and composition.
We have determined the correlation length of composition fluctuations using viscosity measured with a modified Hoeppler viscometer. In transition of the system from the disordered into the bicontinuous microemulsion phase by cooling, the correlation length exhibits a distinct maximum characteristic of the appearance of the microemulsion.
Dynamic properties of lamellar block copolymer phases: X-ray and dynamic light scattering
Petr ŠTĚPÁNEK, Frédéric NALLET‡, Kristoffer ALMDAL¤
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague, Czech Republic
‡Centre de recherches Paul-Pascal, CNRS, Avenue du Docteur Schweitzer, F-33 600 Pessac, France
¤The Danish Polymer Centre, Risø National Laboratory, DK-4000 Roskilde, Denmark
Scattering of synchrotron radiation and dynamic light scattering were used to evaluate the elastic constants of bulk symmetric diblock copolymers in the lamellar phase. Disoriented samples exhibit polycrystalline structure with grains of size of several m. Oriented samples were prepared where the orientation of the macroscopic optical axis with respect to the scattering vector can be selected. Several dynamic modes have been identified by light scattering which correspond to cluster diffusion, self-diffusion of block copolymer chains and undulation of the lamellar planes of the ordered phase. The splay elastic modulus K was determined from the relaxation frequency of the undulation mode. X-ray scattering using synchrotron radiation allowed us to study the diffuse scattering in the vicinity of the Bragg peak of the lamellar structure. Its profile is described by the Caillé exponent ~ (KB)-1/2 thus from known values of the splay elastic constant, K, the compression elastic modulus, B, of the lamellar planes can be evaluated.
On-line rheometry and Small Angle X-Ray Scattering
P. Panine and T. Narayanan
European Synchrotron Radiation Facility, BP220, 38043 Grenoble Cedex
e-mail : panine@esrf.fr
Simultaneous monitoring of rheological parameters and microstructure is a primordial step in understanding the structure and rheology of complex fluids. We have developed a SAXS-rheometer based on a commercial instrument (HAAKE) in the couette flow geometry having an operating temperature range of 10 – 150 ° C and stability ± 0.05° C. This apparatus can be used in either continuous or oscillatory shear modes with imposed stress or shear. We have used this device for the study of shear induced crystallization of a weakly flocculated colloidal latex system. We obtained nearly single-crystalline domains by applying an oscillatory shear of constant deformation and a critical frequency which anneals the stacking faults. We observed that the viscosity of the sample decreased before the crystalline structure emerged. This finding directly confirms that a shear-thinning occurs prior to crystallization in bundle-like ordering. Finally, this apparatus can be used to address a wide range of problems in complex fluids, such as lamellar-to-vesicle transition, order-disorder transition, polymer crystallization, etc.
Recent Achievements in SWAXS Measurements at High-Pressures
M. Steinharta, M. Kriechbaumb, H. Amenitschb, S. Bernstorffc, P. Laggnerb, J. Baldriana, R. Triolod
aInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague
bInstitute of Biophysics and X-Ray Structure Research, Austrian Academy of Sciences, Graz
cSincrotrone Elettra, Trieste, Italy
dDipartimento di Chimica-Fisica, Università di Palermo, Italy
An instrument to facilitate small- and wide-angle X-ray scattering measurements of phenomena induced in samples by elevated hydrostatic pressure as well as by pressure variations including jumps has been constructed [1,2] and is being used for several kinds of experiments [3] at the Elettra synchrotron in Trieste.
A pressure range from atmospheric up to 0.25 GPa (2.5 kbar) can be employed. The pressure is transferred by means of liquid or gaseous pressurising medium to an X-ray sample cell. The cell has two beryllium or diamond windows. Scattering can be observed at angles up to 30O. The sample consistency can range from solid to liquid. The optical path-length ranges from 0.5 up to 4 mm.
The device is PC controlled and integrated into the channel control and data acquisition system. Static measurements at elevated pressures and in addition time-resolved experiments with the time resolution down to the milliseconds range can be performed.
Among the problems studied recently with the use of the high-pressure instrument the most important are barotropic phase transitions in lipid/water systems (DOPE, DPPC), pressure induced crystallizations of polymer blends (PEO, PMMA) and investigations of aggregation phenomena of block co-polymers in supercritical CO2. Beside measurements on bulk samples also grazing incidence experiments using silicon wafer with highly aligned samples are carried out. More detailed description of some interesting results of these studies are presented.
[1] K. Pressl, M. Kriechbaum, M. Steinhart, and P. Laggner, Rev. Sci. Instrum., 68, 4588-4592 (1997).
[2] M. Steinhart, M. Kriechbaum, K. Pressl, H. Amenitsch, P.Laggner, and S. Bernstorff, Rev. Sci. Instrum., 70, 1540-1545 (1999).
[3] see Annual Report of the Austrian SAXS Beamline at Elettra, Trieste (1996-7, 1998,1999)
Research was supported by the Grant Agency of the Czech Republic (grant No:106/99/0557).
THE LAMELLAR ORIENTATION IN THIN DIBLOCK COPOLYMER FILMS
C.M. PAPADAKISa, P. BUSCHa, F. KREMERa, D. POSSELTb, D. SMILGIESc
aFakultät für Physik und Geowissenschaften, Universität Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany
b Department of Mathematics and Physics (IMFUFA), Roskilde University, P.O. Box 260, DK-4000 Roskilde, Denmark
cCHESS Wilson Lab, Cornell University, Ithaca, NY 14853, USA
Compositionally symmetric diblock copolymers in the bulk form a lamellar structure with the lamellar thickness increasing with molar mass. We have studied thin films of a series of symmetric polystyrene-polybutadiene (PS-PB) diblock copolymers only differing in the overall molar mass. Films were spin-coated onto silicon from solution and annealed. Combining tapping mode AFM with grazing-incidence small-angle X-ray scattering (GISAXS) and X-ray reflectometry, we find three regimes: For low molar masses, we observe a flat surface topography and Bragg-peaks in the reflectivity curves, indicating parallel lamellae. For high molar masses, the lamellae are perpendicular to the surface, as evidenced by a lamellar surface texture and an out-of-plane Bragg-rod (Fig. 1). For intermediate molar masses, coexisting lamellar domains of different tilt angles are formed, as seen from AFM and the bending of the out-of-plane Bragg-rod. We attribute this behavior to the fact that the polymer concentration where the transition from the disordered to the lamellar state takes place during spin-coating depends on molar mass: For high molar mass polymers the lamellar structure is formed at a high solvent content and therefore the difference in surface tensions of the two blocks is low, leading to the perpendicular orientation.
Fig. 1: Surface topography (3´ 3 μm scan size, z-range 25.2 nm) and logarithmic out-of-plane GISAXS intensity of a thin film of a PS-PB diblock copolymer sample having a molar mass of 183 kg/mol.
SELF-ORGANIZATION IN SOL-GEL POLYMERIZATION OF ORGANIC-INORGANIC SYSTEMS FOLLOWED BY SAXS
H.KAMIŠOVÁ, D.HLAVATÁ, B.MEISSNER, L.MATĚJKA
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovský Sq.2 CZ-162 06 Prague 6, Czech Republic
Organo-inorganic (O-I) hybrid polymers prepared by sol-gel polymerization have become an object of a concentrated study in the last years. The structure and properties of the hybrid polymers are strongly dependent on the system morphology and interphase interactions. A way to enhance the interphase interaction is the synthesis of O-I polymers from O-I molecular precursors.
Organotrialkoxysilanes RSi(OR’)3 serve as suitable O-I precursors assuring a strong covalent bonding between forming organic and inorganic domains. The sol-gel polymerization of the trialkoxysilanes consists in hydrolysis and subsequent condensation leading to the formation of silsesquioxane clusters. During the reaction microphase separation takes place and gelation of the system may occur.
By SAXS and WAXS, we have studied the structure evolution during the sol-gel polymerization of various organotrialkoxysilanes and found the crucial effect of catalysis in the sol-gel process and of the length of the organic substituent R. While trialkoxysilane with a short R forms a network, the long substituent promotes intramolecular reaction, formation of polyhedral compact structures and a spontaneous self-organization. The microphase separation results in a micellar-like regular arrangement with a correlation distance controlled by the size of the substituent. The most organized arrangement was found in the trialkoxysilanes substituted with long PEO chains, which crystallize and force the silsesquioxane domains to align in the lamellar structure.
Acknowledgement : This work was supported by the Grant Agency of the Academy of Sciences of the Czech Republic (A40500008).
SYNTHESIS AND INTERCROSSLINKING OF FUNCTIONAL ORGANOSILICON MICROGEL PARTICLES
E. BOGDAN, W. JASIŇSKI*, M. MASLYK-WALCZAK**, M.ŠPÍRKOVÁ, P.KADLEC, F.LEDNICKÝ, D.HLAVATÁ, L.MATĚJKA
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovský Sq.2 CZ-162 06 Prague 6, Czech Republic
*present address : University-GH Siegen, D-57068 Siegen, Germany
** present address : Rzeszow University of Technology, 35-959 Rzeszow, Poland
Well-defined heterogeneous polymer networks were prepared by intercrosslinking of functional microgel particles with telechelic polymers.
Synthesis and characterization of microgels.
The functional organosilicon micronetworks were prepared by microemulsion polymerization of trialkoxysilanes.1 Synthesis was carried in two steps: (a) sol-gel polymerization of methyltrimethoxysilane resulting in silsesquioxane micronetwork core and (b) copolymerization with organofunctional trialkoxysilane forming a functional shell of the micronetwork. Microgel particles with vinyl and methacryloyl functionalities were prepared using vinyltrimetoxysilane and (3-methacryloyloxy- propyl)trimethoxysilane monomers. The micronetworks were characterized using static and dynamic light scattering and SAXS. Depending on the reaction conditions, functional particles with Rh = 5-40 nm, M~2*106 and a high average functionality, f=600-3000, were prepared.
Intercrosslinking of microgels
The functional microgel particles dispersed in an organic solution were intercrosslinked with telechelic polymers of various molecular weights: (a) by hydrosilylation with PDMS or (b) by reaction with NH2-terminated PPO.
Characterization of the heterogeneous macronetworks
The structure, morphology and mechanical properties of the networks were characterized using SAXS, TEM and DMA.
Reference
1. F.Baumann, B.Deubzer, M.Geck, J.Dauth, S.Sheiko, M.Schmidt, Adv. Mater. 9, 955 (1997)
Acknowledgement : This work was supported by the Grant Agency of the Academy of Sciences of the Czech Republic (A40500008) and the Grant Agency of the Czech Republic (203/01/0735).
Determination of the number-average molecular weight of polymers by size exclusion chromatography with dual light-scattering/concentration detection
Miloš Netopilík1, Štěpán Podzimek2 and Pavel Kratochvíl1
1Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague, Czech Republic
2SYNPO, 532 07 Pardubice, Czech Republic
A new method [1] for the estimation of the weight-to-number-average molecular-weight ratio of polymers with a narrow molecular-weight distribution, approximated by log-normal distribution, using size-exclusion chromatography (SEC) with concentration and light-scattering detectors. From experimental data, the ratios are calculated by application of two procedures: one using the concentration and light-scattering elution curve for the polymer measured, and the other based on the concentration elution curve and calibration line for a wide range of molecular weights. An iteration method has been developed making the two ratios of the weight-to-number averages converge. The method was applied to a series of narrow molecular-weight distribution polystyrene standards.
Acknowledgments
The authors gratefully acknowledge the temporary loan of a miniDAWN laser photometer from the Wyatt Technologies Ltd. as well as support of the Academy of Sciences of the Czech Republic (grant number K 205 0602).
Literature
[1] Miloš Netopilík, Štěpán Podzimek and Pavel Kratochvíl, J. Chromatogr., accepted for publication
Phase Behaviour of Block Copolymers in Solution
A. Norman*, J. P.A. Fairclough, S. Mai, S. Turner, C. Booth, A. J. Ryan
Block copolymers of oxyethylene and oxybutylene were prepared at the University of Manchester by living anionic polymerization. These polymers were dissolved in water to form micelles. As the concentration of polymer is increased the micelles pack together to form gel networks. The gel networks have a variety of structure, which is temperature and concentration dependent. Structures that have been deduced are Cubic (both body-centered and face-centered), Hexagonal and Lamella.
The purpose of this work is to construct phase diagrams of these block copolymer solutions, and then calculate the kinetics of the phase transitions that can occur by heating or cooling the gel.
Techniques of characterization include Optical Microscopy, Rheology, and Small angle X-Ray Scattering, (SAXS).
This work will concentrate more on the SAXS performed at the SRS Daresbury Laboratory and at the ESRF. Simultaneous SAXS/WAXS/DSC has been performed at both synchrotron sources, and the effect of shear on the copolymers was investigated during the SAXS experiments using a couette cell at beamline 16.1 of the Daresbury Laboratory using the RAPID small angle detector.
Architectural effects of block copolymer phase behaviour
S.C. Turner, J. Xu, S. Mai, J.P.A. Fairclough, A.J. Ryan
Department of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF
C. Chaibundit, W. Mingvanish, A.J. Ryan, C. Booth
Department of Chemistry, University of Manchester, Oxford
Road, Manchester,
M13 9PL
It has been known for some time that the molecular architecture at constant chain length and composition will dramatically influence the processes of microphase separation and crystallisation, and consequently the physical properties in block copolymers. The effect of block copolymer architecture on these important processes has been studied in terms of triblock and diblock copolymers of oxyethylene(E) /oxybutylene (B) systems.
Each architecture showed classical ordered phase behaviour, however between the classical phases the complex gyroid morphology was also stable at weak segregations. This work manifested a higher stability for the gyroid phase above the hexagonal perforated lamellar phase that suffers from large degrees of packing frustration. Significant results are also confirmed in terms universality of the Flory-Huggins equation irrespective of architectural difference and the effect on domain length scale.
B. Shaw
Investigating the Structure of Block Co-polymer Gels
Abstract not supplied
P. Matějíček, F. Uhlík, Z. Limpouchová, K. Procházka, Z.
Tuzar, S.E. Webber
Hydrophobically Modified Amphiphilic Block Copolymer Micelles in
Aequous Media
Available in the supplement to printed programme booklet only.
K. Podhájecká, M. Štěpánek, K. Procházka, Z. Tuzar, W.
Brown
Hybrid Polymeric Micelles with Hydrophobic Cores and Mixed
Polyelectrolyte/Nonelectrolyte Shells in Aequous Media
Available in the supplement to printed programme booklet only.