Inversion of Circular Dichroism Signals in Chiral Polythiophene Films Induced by End-On-Oriented Surface-Segregated Monolayers

Abstract

A chiral polythiophene surfactant based on poly­(3-(S)-2-methylbutylthiophene) ((S)-P3MBT) with a semifluoroalkyl group at one end of the main chain was synthesized and used to form surface-segregated monolayers (SSMs). Films of pure (S)-P3MBT mainly adopted the edge-on orientation, whereas (S)-P3MBT films with a SSM of the polymer surfactant (S)-P3MBT-F17 contained a large proportion of end-on-oriented polythiophene, both at the surface and inside the films. The thin films with the SSM showed circular dichroism signals, with the sign opposite to those observed in (S)-P3MBT films. These findings suggest that the orientation-controlled SSM layers induced changes in the packing of the polymer aggregates in the films, resulting in a dramatic change in the excitonic interactions of the chiral semiconducting polymers.

Polymeric Indolenine–Squaraine Foldamers with a Preferred Helix Twist Sense and Their Chiroptical Absorption and Emission Properties

“…The most prominent example is DNA, which is a polymer consisting of achiral bases linked to a chiral backbone containing deoxyribose, thus giving rise to a homohelical macrostructure . Inspired by this, many artificial homohelical polymers consisting of a wide variety of different parent monomer structures have been synthesized and studied, − includingbut not limited tophenylene ethynylenes, − thiophenes, − indolocarbazoles, aromatic amides, − porphyrins, synthetic peptides, , bi- , and terpyridines, terphenyls, , isocyanates, − isocyanides, − silanes, , and acetylenes. − The homohelicity in these foldamers was realized using different approaches. Apart from utilizing intrinsically chiral monomers to construct the main chain, − an excess in preferred screw sense can be attained by the introduction of a chiral guest molecule, ,,, the use of chiral solvents, using chiral terminal groups, ,,, asymmetric polymerization, , chiral resolution, ,, or the incorporation of chiral units into the main chain. ,, However, one of the most established methods is the addition of an element of chirality onto the peripheral side chain, which then promo...…”