Enhancing Long-Range Ordering of P3HT by Incorporating Thermotropic Biphenyl Mesogens via ATRP

The methoxybiphenyl liquid crystalline mesogen 6-((4′-methoxy-[1,1′-biphenyl]-4-yl)oxy)hexyl methacrylate (MeOBP) was incorporated into block copolymers with regioregular poly(3-hexylthiophene) (P3HT) by a combination of Grignard metathesis (GRIM) and atom transfer radical polymerization (ATRP) techniques. Side chain engineering with a thermotropic liquid crystalline segment produced an improved morphology resulting in field-effect mobilities of ∼10–2 cm2/(V s) measured in organic thin film transistors (OTFTs). It was observed that improved π–π stacking distances between edge-on oriented polythiophene segments upon annealing facilitated charge transport which was accomplished with π–π stacked biphenyl mesogens with P3HT block. Variation of surface morphology of polymer thin films upon annealing was investigated by tapping mode atomic force microscopy (TMAFM). A combined study of differential scanning calorimetry (DSC) and polarized optical microscopy (POM) was also performed to identify liquid crystalline...