Unique polymorphism of oligothiophenes

Quarterthiophenes with long pendant alkyl side-chains exhibit a unique, hitherto unreported polymorphism arising from side-chain comformational changes. Those with long backbone structures show two different side-chain conformation ally induced polymorphs, one with a fully extended side-chain and one with a bent side-chain conformations. This unique polymorphism is a result of subtle differences in molecular architecture and can be induced by crystallization conditions.