期刊
MACROMOLECULAR THEORY AND SIMULATIONS
卷 12, 期 8, 页码 549-559出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/mats.200350014
关键词
PEO; phase separation; PNIPAM; polymer brushes; water-soluble polymers
The quality of solvents of polymers is often described in terms of the Flory chi parameter typically assumed to depend only on the temperature T. In certain polymer-solvent systems fitting the experimental data enforces the replacement of chi(T) by a concentration-dependent chi(eff). In turn, this modifies the swelling and collapse behavior. These effects are studied, in the framework of a mean-field theory, for isolated coils and for planar brushes. The phi dependence of chi(eff) gives rise to three main consequences: (i) shift in the cross-over between Gaussian and self-avoidance regimes; (ii) a possibility of first-order collapse transition for isolated flexible coils; (iii) the possibility of a first-order phase transition leading to a vertical phase separation within the brush. The discussion relates these effects directly to thermodynamic measurements and does not involve a specific microscopic model. The implementation for the case of poly(N-isopropylamide) (PNIPAM) brushes is discussed.
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