Coarse-graining diblock copolymer solutions: a macromolecular version of the Widom-Rowlinson model

TL;DR

This paper introduces a systematic coarse-graining method for diblock copolymer solutions, simplifying blocks to single soft blobs and deriving effective interactions to study microphase separation.

Contribution

It develops a novel coarse-grained model for diblock copolymers using effective potentials derived from Monte Carlo simulations, enabling efficient analysis of phase behavior.

Findings

Effective intra- and intermolecular potentials were successfully extracted.

The model captures microphase separation driven by block incompatibility.

The approach simplifies complex polymer interactions for computational studies.

Abstract

We propose a systematic coarse-grained representation of block copolymers, whereby each block is reduced to a single ``soft blob'' and effective intra- as well as intermolecular interactions act between centres of mass of the blocks. The coarse-graining approach is applied to simple athermal lattice models of symmetric AB diblock copolymers, in particular to a Widom-Rowlinson-like model where blocks of the same species behave as ideal polymers (i.e. freely interpenetrate), while blocks of opposite species are mutually avoiding walks. This incompatibility drives microphase separation for copolymer solutions in the semi-dilute regime. An appropriate, consistent inversion procedure is used to extract effective inter- and intramolecular potentials from Monte Carlo results for the pair distribution functions of the block centres of mass in the infinite dilution limit.