Microphase Separation Induced by Differential Interactions in Diblock Copolymer/Homopolymer Blends

TL;DR

This paper presents a theoretical study of phase behavior in diblock copolymer/homopolymer blends, revealing a unique closed-loop microphase separation driven by differential interactions despite binary miscibility.

Contribution

It introduces the concept of a closed-loop immiscible region in AB/C blends caused by differences in A/C and B/C interactions, highlighting a new mechanism for microphase separation.

Findings

A closed-loop immiscible region exists despite binary miscibility.

Microphase separation occurs within this loop, forming various ordered structures.

Stronger interactions between the homopolymer and one block enhance phase separation.

Abstract

Phase behavior of diblock copolymer/homopolymer blends (AB/C) is investigated theoretically. The study focuses on a special case where all three binary pairs, A/B, B/C and C/A, are miscible. Despite the miscibility of the binary pairs, a closed-loop immiscible region exists in the AB/C blends when the A/C and B/C pair interactions are sufficiently different. Inside the closed-loop, the system undergoes microphase separation, exhibiting different ordered structures. This phenomenon is enhanced when the homopolymer (C) interacts more strongly to one of the blocks (A or B).