Collapse of polymer brushes grafted onto planar ... - Wageningen UR

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PHASE TRANSITIONS OF BINARY POLYMER MIXTURES CONFINED BETWEEN COMPETING SURFACES K. Binder, M. Müller Institut für Physik, Johannes-Gutenberg-Universität Mainz, Staudinger Weg 7, 55099 Mainz, Germany e-mail: kurt.binder@uni-mainz.de; marcus.mueller@uni-mainz.de ABSTRACT A symmetrical polymer blend (chain lengths NA = NB = N ) is considered in a thin film geometry, treating the case where one surface preferentially attracts component A, while the other surface attracts component B. This situation leads to an interesting competition between lateral versus perpendicular phase separation between an A-rich and a B-rich phase, which is studied both with the self-consistent field theory and with Monte Carlo simulations of the bond fluctuation model on the simple cubic lattice [1-5]. For simplicity, the case of “antisymmetric walls” (same strength of the surface forces) is emphasized, while the general case of asymmetric surfaces is treated only briefly. It is argued that the increase of the Flory- Huggins χ parameter that drives phase separation in the bulk (if χ > χcb = 2/N in the mean field limit) leads to a rounded transition from a uniformly mixed state to a stratified structure in the thin film geometry (an A-rich phase is separated from the B-rich phase by a single interface, while in the case of “symmetric” walls which both attract the same component a stratified structure with two interfaces parallel to the walls results). Only for a distinctly larger value χc (D), controlled by the strength of the wall-monomer interactions and related to the wetting transition of a semi-infinite polymer blend, is a sharp phase transition encountered, related to lateral phase separation. For the case where in the semi-infinite geometry one has first-order wetting, the thin film shows a triple point, and two critical points appear as remnants of prewetting criticality. For asymmetric surfaces forces, the triple point can merge with one of the critical points, and a phase diagram with a single critical point remains. Also tricritical phenomena in thin films may occur. Ginzburg criteria are developed for a discussion of the validity of the mean field description. Finally, also some comments on related experiments [6] are made. References 1. Müller, M. and Binder, K., 1998. Macromolecules 31, 8323. 2. Müller, M, Binder, K. and Albano, E. V., 2000. Europhys. Lett 49, 724. 3. Müller, M, Binder, K. and Albano, E. V., 2000. Physica A279, 188. 4. Müller, M, Albano, E. V. and Binder, K., 2000. Phys. Rev. E62, 5281. 5. Müller, M. and Binder, K., 2001. Phys. Rev. E63, 021602. 6. Kerle, T, Klein, J. and Binder, K., 1996; 1999. Phys. Rev. Lett. 77, 1318; Europ. Phys. J. B7, 401.
SWEET BRUSHES: SYNTHESIS AND INTERFACIAL BEHAVIOUR OF POLYSTYRENE- POLYSACCHARIDE DI-BLOCK COPOLYMERS W.T.E. Bosker 1) , K. Ágoston 2) , M.A. Cohen Stuart 1) , W. Norde 1) , J.W. Timmermans 2) , T.M. Slaghek 3) 1) Department of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands 2) Agrotechnological Research Institute ATO, Wageningen UR, 6700 AA Wageningen, The Netherlands 3) TNO Nutrition and Food Research, 3704 HE Zeist, The Netherlands email: bosker@fenk.wau.nl ABSTRACT Research has revealed that coating surfaces with hydrophilic polymer brushes can prevent or reduce protein adsorption and hence retard biofouling. In biological systems the use of natural polymers may be preferred and polysaccharides seem to be the most plausible candidate. Linear block copolymers of polystyrene and polysaccharide were synthesized using a block synthesis method with amino terminated polystyrene and sodium cyanoborohydride as reducing agent. Different types of polysaccharides, dextrans and maltodextrins, with various molecular weights were used. IR spectroscopy indicated a successful coupling. Yields are 75 to 95 wt%. Interfacial pressure measurements of monolayers of the copolymers showed hysteresis between successive compression and expansion cycles. This is, to a large extent, due to the slow adsorption/desorption of the polysaccharide chains at the air-water interface and the formation of aggregates of copolymer at the interface, mainly by H-bonding between adjacent polysaccharide chains. When the time scale of compression and expansion is increased the hysteresis becomes smaller and reaches a time independent level, demonstrating a permanent change in conformation of the copolymers. The relaxation time for hysteresis is 85 minutes. Interfacial pressure isotherms differ from theoretical polymer brush model predictions. The deviation is attributed to the relative short length of the polysaccharide chains.
Page 1 and 2: Frontis - Wageningen International
Page 3 and 4: Prof. dr. Hans Fraaije Leiden Unive
Page 5 and 6: Prof. Ullrich Steiner University of
Page 7 and 8: Preface Self-consistent field model
Page 9 and 10: covered by polymers), and R. Rajago
Page 11 and 12: FIRST-ORDER WETTING TRANSITION AT F
Page 13 and 14: MOLECULAR SCF MODELLING OF PORES IN
Page 15 and 16: COLLAPSE OF POLYMER BRUSHES GRAFTED
Page 17: SURFACE FORCES, SUPRAMOLECULAR POLY
Page 21 and 22: EFFECT OF MIXING OF TWO CHARGED PHO
Page 23 and 24: Figure 2 show a semi-log comparison
Page 25 and 26: MODELING OF STATIONARY POLYMER DIFF
Page 27 and 28: THEORY AND SIMULATION OF BILAYER ME
Page 29 and 30: Figure 1. Time evolution of the she
Page 31 and 32: SALT EFFECT TO RAYLEIGH DROPLETS OF
Page 33 and 34: MACROMOLECULES AT INTERFACES, A FLE
Page 35 and 36: APPLICATION OF HETEROGENEOUS LATTIC
Page 37 and 38: 8. Linse, P., 1993b. Phase behavior
Page 39 and 40: MODELING INTERFACIAL EFFECTS ON THE
Page 41 and 42: Using this patterned electrode, we
Page 43 and 44: span the gap between the electrodes
Page 45 and 46: desirable to use a probe with a muc
Page 47 and 48: span the gap between the electrodes
Page 49 and 50: MEMBRANE FUSION: RESULTS FROM SIMUL
Page 51 and 52: the transition temperature T * when
Page 53 and 54: PROTEIN ADSORPTION ON SURFACES WITH
Page 55 and 56: MODELLING STRUCTURE AND ADHESION AT
Page 57 and 58: References 1. Fischel, L.B. and The
Page 59 and 60: MULTIDOMAIN CONFORMATIONS OF RANDOM
Page 61 and 62: SUPRAMOLECULAR COORDINATION POLYMER
Page 63 and 64: INFLUENCE OF POLYMERS ON THE BENDIN
Page 65 and 66: SPINODAL DECOMPOSITION IN BINARY PO
Page 67 and 68: PERSISTENCE LENGTH OF WORM-LIKE MIC
Page 69 and 70:
For small particles with radius R <
Page 71:
MEAN-FIELD THEORY FOR THE ADSORPTIO
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