Molecular simulation of 2-dimensional microphase separation of single-component homopolymers grafted onto a planar substrate

TL;DR

This study uses molecular Monte Carlo simulations to explore microphase separation in polymer brushes grafted onto a substrate, revealing diverse lateral domain patterns akin to diblock copolymer melts.

Contribution

It demonstrates that grafted homopolymers exhibit microphase separation and diverse domain patterns under certain conditions, extending understanding of polymer brush phase behavior.

Findings

Microphase separation occurs in grafted homopolymers under specific parameters.

Various lateral domain patterns similar to diblock copolymer melts are observed.

Grafting constraints prevent macrophase separation, promoting microphase separation.

Abstract

The structural phase behavior of polymer brushes, single-component linear homopolymers grafted onto a planar substrate, is studied using the molecular Monte Carlo method in 3 dimensions. When simulation parameters of the system are set in regions of macrophase separation of solution for the corresponding non-grafted homopolymers, the grafted polymers also prefer segregation. However, macrophase separation is disallowed due to the spatially-fixed grafting points of the polymers. Such constraints on the grafting are similar to connecting points between blocks of non-grafted diblock copolymers at the microphase separation in the melt state. This results in "microphase separation" of the homopolymer brush in the lateral direction of the substrate. Here we extensively search the parameter space and reveal various lateral domain patterns that are similar to those found in diblock copolymer melts at microphase separation.