Intense Chiral Optical Phenomena in Racemic Polymers by Cocrystallization With Chiral Guest Molecules: A Brief Overview

Abstract

This review is devoted to the chiral optical behavior of films of racemic polymers whose chirality is induced by cocrystallization with nonracemic (also temporary) guest molecules. We provide examples of macromolecular amplification of chirality, produced by molecular and supramolecular mechanisms, on industrially relevant polymers like poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) and syndiotactic polystyrene (s-PS).

Recent Trends in Chiroptical Spectroscopy: Theory and Applications of Vibrational Circular Dichroism and Raman Optical Activity

“…If it is doped with a small chiral molecule, the chirality can be propagated in a non-linear way and the whole system becomes optically active. [141,142] This was observed for poly(4carboxyphenyl)doped with chiral amines, [143,144] poly(2,6-dimethyl-1,4-phenylene)doped with α-pinene, [145] and other systems. [146][147][148][149] In many cases, the optical activity remains even after removal of the chiral dopant, i. e., the system "remembers" the chiral perturbation.…”

“…An achiral polymer usually forms short helical segments. If it is doped with a small chiral molecule, the chirality can be propagated in a non‐linear way and the whole system becomes optically active . This was observed for poly(4‐carboxyphenyl)doped with chiral amines, poly(2,6‐dimethyl‐1,4‐phenylene)doped with α‐pinene, and other systems .…”

Chirality on Amorphous High-Tg Polymeric Nanofilms: Optical Activity Amplification by Thermal Annealing

“…It is worth noting that the induction of helical handedness in polymers [ 28 ] can be exploited in the design of optical devices or for data storage, other than because of its relevance to chiral amplification [ 5 , 29 , 30 , 31 ]. Several studies were reported for different systems both in solution [ 32 ] and in the solid state [ 31 , 33 , 34 ]. For example Green and co-workers reported the possibility for inducing a helical conformation with a prevailing screw sense in polyisocyanates in dilute solution by functionalization of the macromolecules with chiral pendant groups having a small enantiomeric ratio [ 5 , 35 ] or by photoresolution [ 36 ].…”

“…Furthermore, recently Guerra et al, investigated the chiroptical response of racemic polymers in the solid state which are able to form co-crystalline phases with chiral low-molecular-weight guests [ 33 ]. This phenomenon can be produced by molecular and supramolecular mechanisms which are of configurational and conformational origin.…”