Domain Structures of Poly(3-dodecylthiophene)-Based Block Copolymers Depend on Regioregularity

Abstract

Microphase-separation behavior of conjugated–amorphous block copolymers (BCPs) is driven by a complex interplay between Flory–Huggins interaction (χ), liquid crystalline (LC) interaction, and crystallization. Herein, in order to elucidate the influence of LC interaction on the morphology of the BCPs, we report the effects of regioregularity (RR) on the microphase separation and molecular packing structures of poly(3-dodecylthiophene)-block-poly(2-vinylpyridine) (P3DDT-b-P2VP). To decouple the effect of LC interactions from crystallization kinetics, we investigate the morphological behavior of the P3DDT-b-P2VP at above the melting temperature of P3DDT (∼160 °C). Both electron microscopy and X-ray scattering show an abrupt reduction in the domain spacing of both lamellar and cylindrical phases as the RR of P3DDT block increases. Specifically, lower RR (i.e., 85, 79, and 70%) BCPs have larger domain spacings than high RR (94%) by 50% (lamellar) or 80% (cylindrical), even though the overall molecular weights ...