Fluctuation Effects on Microphase Separation in Random Copolymers

TL;DR

This paper investigates how fluctuations influence microphase separation in random copolymers, revealing that fluctuations can stabilize the disordered phase at finite temperatures and induce a weak first-order transition to an ordered phase.

Contribution

It demonstrates the significant role of fluctuations in the phase behavior of random copolymers, extending mean field theory with a fluctuation analysis similar to Brazovskii's weak crystallization theory.

Findings

Fluctuations cause the disordered phase to be locally stable at all finite temperatures.

A weak first-order transition to an ordered phase occurs below a certain temperature.

The inverse propagator has a minimum at non-zero wave-numbers, indicating microphase formation.

Abstract

We study random copolymers consisted of two kinds of monomers with attraction between similar kinds. The mean field analysis of this system indicates a continuous phase transition into a phase with periodic microdomain structure. It is shown that the inverse of the renormalized propagator has a minimum at non-zero wave-numbers. Consequently, there is an anomalously large contribution of fluctuations that make the disordered phase locally stable at every finite temperature. However, below a certain temperature, the ordered phase is shown to be locally stable and a weak first order transition is possible, similar to the weak crystallization theory developed by Brazovskii.