Tuning Mechanical and Optoelectrical Properties of Poly(3-hexylthiophene) through Systematic Regioregularity Control

Abstract

While the regioregularity (RR) of conjugated polymers is known to have a strong influence on their inherent properties, systematic study of the RR effect has been limited due to the lack of a synthetic methodology. Herein, we successfully produced a series of poly(3-hexylthiophene)s (P3HTs) having a wide range of RR from 64 to 98%. Incorporation of controlled amounts of head-to-head (H–H) coupled dimer in modified Grignard metathesis polymerization allows a facile tuning of the RR of the P3HTs with comparable molecular weight and low polydispersity. Then, we investigated the effect of RR on structural, electrical, and mechanical properties of P3HTs in which a higher content of H–H regio-defects, namely lower RR, systematically lowered the degree of crystallinity. Although high RR P3HT (98%) had higher charge carrier mobility (1.81 × 10–1 cm2 V–1 s–1), its strong crystallinity induced high brittleness and stiffness, resulting in device failure under a very small strain, as shown in tensile and bending test...