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 conformationally 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.