Solvent response of diblock copolymer brushes

摘要

We have performed continuum self-consistent field (SCF) calculations to study the solvent responseof diblock copolymer A-B brushes, where all copolymer chains are grafted onto a flat andimpenetrable substrate and immersed in a solvent. In order to avoid the numerical problemassociated with the δ-function initial condition specifying that all A-ends are grafted at a smalldistance from the impenetrable substrate, we numerically integrate the Chapman–Kolmogorovequations, rather than solving the modified diffusion equations, when chains are strongly stretched(e.g., at a high grafting density or in a good solvent). This gives much better numerical performanceof SCF calculations in such cases. The solvent response of the diblock copolymer brushes ischaracterized by the changes in brush height and surface-layer composition (i.e., relative fraction ofA segments in the copolymers present in the region above the brush height) in three differentsolvents: Neutral, A-like, and B-like. We have systematically studied the influence of copolymercomposition, copolymer chain length, chain-grafting density, and A-B incompatibility on the solventresponse of diblock copolymer brushes. Our results are in good agreement with availableexperiments and can provide some guidance to the design of smart surfaces from diblock copolymerbrushes best suited for targeted applications.