Self-assembly of fully conjugated rod–rod diblock copolymers within nanofibers

Abstract

We report the fabrication and self-assembly study of electrospun nanofibers of oligothiophene-block-oligophenylenevinylene, a fully conjugated rod–rod diblock copolymer (BCP). X-ray scattering and transmission electron microscopy of microtomed sections of nanofibers and solution-cast films revealed the formation of hierarchical self-assembly, consisting of BCP micro-phase separation at the length scale of 5 nm and molecular ordering within individual conjugated blocks at the length scale of 0.4–1.6 nm. Extensional flow during electrospinning transforms the curved BCP morphology (in films) into a lamellar morphology in nanofibers oriented along the axis. In addition, electrospinning induces a partial inter-digitation of side chains resulting in a unique thiophene phase with two distinct populations of π–π stacking structures at the molecular sub-nanometer level. To our knowledge, this is the first ever study to investigate the self-assembly of fully conjugated rod–rod block copolymers within nanofibers, a material system with the potential to revolutionize the field of wearable photovoltaics.