Controlling the Condensed Structure of Polythiophene and Polyselenophene-based All-conjugated Block Copolymers

Block copolymers can microphase separate into a variety of well-defined nanoscale structures. Conjugated polymers are a kind of semi-rigid macromolecules with special mechanical, conducting, and optoelectronic properties. All-conjugated block semiconducting copolymers have gained immense interest because they combine the optoelectronic properties of conjugated polymers with the fascinating self-assembly properties of block copolymers. In this feature article, we introduced some research progresses on poly(3-alkylthiophene) and poly(3-alkylselenophene)-based all-conjugated diblock copolymers, focusing on controlling the condensed structure of these two systems in our group. By tuning their molecular structures (such as main/side chains, the length of alkyl side chains and side substitutions, etc.), and the post-treatment in their solution and film states (such as changing solvents, aging, thermal and solvent annealing, etc.), the synergy and competition between two basic phase transitions, that is, their microphase-separated behavior and crystalline behavior were systematically studied and clarified. As a result, their condensed structures were efficiently tuned. Furthermore, their optoelectronic properties such as charge mobilities based on their different condensed structures were investigated to build up the relationship among their chemical structures, condensed structures, and device performance. As poly(3-alkylthiophene) and poly(3-alkylselenophene) are model systems with simple molecular structures, the rules and knowledge about controlling their condensed structures obtained from these model systems are expected to be applied in other conjugated systems with more complexed molecular structures and better properties.