Stretch-collapse transition of polyelectrolyte brushes in a poor solvent

被引:21
作者
vonGoeler, F
Muthukumar, M
机构
[1] UNIV MASSACHUSETTS,POLYMER SCI & ENGN DEPT,AMHERST,MA 01002
[2] UNIV MASSACHUSETTS,MAT RES SCI & ENGN CTR,AMHERST,MA 01002
关键词
D O I
10.1063/1.472984
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
This paper describes the behavior of charged, polymer brushes in electrolyte solutions of varying solvent quality. The brush height, d, dependence on the chain length, L (=Nl, where I is the Kuhn length), the grafting density sigma, and solvent conditions is determined. We consider a monomer-monomer potential consisting of three components: (1) a long-ranged, screened Coulombic component of strength (v) over bar/l (1 is the Kuhn length) and range kappa(-1); (2) a short-ranged, two-body component of strength <(w)over bar l>; and (3) a short-ranged, three-body component of strength (u) over bar l(3). In particular, we examine the transition from a stretched state to a collapsed state in a poor solvent; (<(w)over bar <0>) as the solvent quality is decreased. Using dimensional analysis, Monte Carlo methods, and a variational technique, a first order transition is observed as predicted by the scaling arguments of Ross et al. and Borisov et al. for high charge/grafting densities. Using a variational procedure, we derive an analytical expression for the brush size and determine, quantitatively, the critical conditions for a first order transition in terms of key dimensionless variables, vN(5/2), kappa lN(1/2), wN(3/2),and uN(2) (where v = 2 pi sigma l(2) (v) over bar, w = sigma l(2) (w) over bar, and u = sigma(2)l(4) (u) over bar. (C) 1996 American Institute of Physics.
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页码:11335 / 11346
页数:12
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