Cooperative Chiral Order in Copolymers of Chiral and Achiral Units

TL;DR

This paper investigates the cooperative chiral ordering in copolymers with chiral and achiral units, using a theoretical model to explain how optical activity depends on composition.

Contribution

It introduces a theoretical mapping of copolymer chiral order onto a one-dimensional random-field Ising model, explaining the observed optical activity behavior.

Findings

Optical activity shows strong cooperativity depending on chiral unit concentration.

The random-field Ising model accurately predicts the optical activity variation.

Chiral order in copolymers can be understood through statistical physics models.

Abstract

Polyisocyanates can be synthesized with chiral and achiral pendant groups distributed randomly along the chains. The overall chiral order, measured by optical activity, is strongly cooperative and depends sensitively on the concentration of chiral pendant groups. To explain this cooperative chiral order theoretically, we map the random copolymer onto the one-dimensional random-field Ising model. We show that the optical activity as a function of composition is well-described by the predictions of this theory.