Molecular assembly and properties of polythiophenes

π-Conjugated polymers are used in many industrial applications and are expected to become an integral part of future electronic and optical technologies. Molecular self-assembly is a promising method for improving the functionality and utility of π-conjugated polymers. The carrier mobility in polymer materials produced by self-assembly is influenced by the morphology and state of molecular assembly in a similar manner to the influence of crystallinity and amorphism in silicon. π-Conjugated polythiophenes with controlled molecular structures and long side chains often form π-stacked structures by self-assembly through side-chain aggregation. Such polythiophenes have higher carrier mobility, optical third-order nonlinear susceptibility and Verdet constant compared with π-conjugated polythiophenes that do not self-assemble. This review covers the development and functionalities of self-assembled π-conjugated polythiophenes with regio-regular head-to-tail, Th(R)–Ar–Th(R) and head-to-head structures with alkynyl side chains.