Multi-scale coarse-graining of diblock copolymer self-assembly: from monomers to ordered micelles

TL;DR

This study develops a multi-scale coarse-graining approach to model diblock copolymer self-assembly, revealing micellization and ordering phenomena from monomers to ordered structures.

Contribution

It introduces a novel two-step coarse-graining method that connects microscopic models to mesoscopic micellar structures, enabling detailed simulation of self-assembly processes.

Findings

Micelles form with an average of 100 copolymers beyond a critical concentration.

A disorder-to-order transition to a cubic phase occurs at higher concentrations.

Effective micelle-micelle interactions are derived from first principles.

Abstract

Starting from a microscopic lattice model, we investigate clustering, micellization and micelle ordering in semi-dilute solutions of AB diblock copolymers in a selective solvent. To bridge the gap in length scales, from monomers to ordered micellar structures, we implement a two-step coarse graining strategy, whereby the AB copolymers are mapped onto ``ultrasoft'' dumbells with monomer-averaged effective interactions between the centres of mass of the blocks. Monte Carlo simulations of this coarse-grained model yield clear-cut evidence for self-assembly into micelles with a mean aggregation number n of roughly 100 beyond a critical concentration. At a slightly higher concentration the micelles spontaneously undergo a disorder-order transition to a cubic phase. We determine the effective potential between these micelles from first principles.