Synthesis of Poly(3-butylthiophene) with Trisiloxane End Group and Its Surface Segregation Behavior in Thin Films

Abstract

A poly(3-butylthiophene) derivative with an end group of 1,1,1,3,3,5,5-heptamethyl trisiloxane group (P3BT-Si) was synthesized for the application of surface segregated monolayer (SSM) in polymer films. The surface segregation behaviors, thermal properties and chain orientation of P3BT-Si were investigated. The formation of the surface layer of P3BT-Si was confirmed in the blend films with polystyrene. In contrast to the fluoroalkylterminated polymer (P3BT-F17) that shows strong end-on orientation in the SSM with high crystallinity, P3BT-Si showed edge-on orientation in the SSM with low crystallinity. The difference can be attributed to the more flexible structure of trisiloxane group than the fluoroalkyl chain.

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

“…For a better understanding of the chiroptical properties in thin films, the material systems with the precise controllability of the film structures such as the orientations and aggregations are highly desired. We have developed semiconducting polymers bearing functional groups with low surface energy, such as fluoroalkyl or oligo­(dimethyl siloxane) chains, which form surface-segregated monolayers (SSMs) on the surface of organic semiconductor films. − The orientation of the polymers in SSMs as edge-on (parallel to the surface) or end-on (vertical to the surface) was controlled by careful molecular design. The edge-on-oriented polymers in the SSM had little effect on the properties of the polymer chains inside the films, − whereas the end-on-oriented polymers had a large effect on the chain orientations, crystalline structure, and film morphology in the bulk of the films through the induction effect from the surface layer. − Based on these results, we decided to introduce a chiral moiety into the polymers for end-on-oriented SSMs to investigate the effects of the SSMs on the packing structures of the chiral polymers inside the films.…”

Phytol-Derived Alkyl Side Chains for π-Conjugated Semiconducting Polymers

“…In fact, the solubility of π-conjugated semiconducting polymers largely relies on alkyl side chains and a large proportion of soluble semiconducting polymers with high performance comprise large amounts of insulating alkyl chains (typically 40–60 wt %). Alkyl side chains also have a significant impact on interchain packing, molecular orientation, and polymer morphology in films, which are features that are known to affect device performance. − The commonly used side chains consist of linear and branched alkyl chains. Linear alkyl chains, such as n -hexyl, n -dodecyl, and n -octadecyl groups, have their own crystalline nature, which can influence intermolecular interactions of the π-conjugated cores and the film crystallinity (known as a fastener effect). , This often facilitates the charge transport in organic semiconducting materials.…”