Self-Consistent Field Theory of Brushes of Neutral Water-Soluble Polymers

TL;DR

This paper develops a self-consistent field theory for neutral water-soluble polymer brushes, incorporating temperature-dependent interactions, and analyzes their structural and force profiles, including effects of vertical phase separation.

Contribution

It formulates a self-consistent field theory using an effective Flory parameter that depends on temperature and concentration, and applies it to model polymer brushes with phase separation.

Findings

Vertical phase separation affects force profiles and concentration distribution.

Presence of a minimum in moments vs. grafting density.

Explicit application to PNIPAM brushes.

Abstract

The Self-Consistent Field theory of brushes of neutral water-soluble polymers described by two-state models is formulated in terms of the effective Flory interaction parameter $\chi_{eff}(T,\phi)$ that depends on both temperature, T and the monomer volume fraction, $\phi$. The concentration profiles, distribution of free ends and compression force profiles are obtained in the presence and in the absence of a vertical phase separation. A vertical phase separation within the layer leads to a distinctive compression force profile and a minimum in the plot of the moments of the concentration profile vs. the grafting density. The analysis is applied explicitly to the Karalstrom model. The relevance to brushes of Poly(N-isopropylacrylamide)(PNIPAM) is discussed.