End-on Chain Orientation of Poly(3-hexylthiophene)-Containing Rod-Rod Diblock Copolymer via Controlled Regioregularity-Induced Microphase Separation

We synthesized amphiphilic poly(3-hexylthiophene)-block-poly(3-(2-methoxyethoxy)methylthiophene) copolymer (P3HT-b-P3MEGT) with a regioregularity (RR) of P3HT block having 82 %. At this RR value, the crystallinity of the P3HT was reduced and the microphase separation prevails over the crystallization effect. The synthesized P3HT-b-P3MEGT showed well-ordered lamellar nanostructures after thermal annealing above the melting point of P3HT block. P3HT-b-P3MEGT thin films showed parallel oriented lamellar nanostructures to the substrate because of a large difference of surface tension between hydrophobic P3HT and hydrophilic P3MEGT. Parallel oriented lamellar nanostructure induced end-on orientation of P3HT and P3MEGT chains, which enhances significantly the vertical hole mobility more than 30 times compared to P3HT continuous thin films with edge-on orientation.