We fabricated end-on orientation, that is, main polymer chains are oriented vertically to the substrate, of amphiphilic poly(3-hexylthiophene)-block-poly(3-(2-methoxyethoxy)methylthiophene) copolymer (P3HT-b-P3MEGT) by controlling regioregularity (RR) of P3HT block. While block copolymers containing P3HT block with RR higher than 85 % showed fibril structure due to the strong π-π interaction of P3HT chains induced by crystallization of P3HT, P3HT-b-P3MEGT with lower RR (82%) showed well-defined microphase separation. P3HT-b-P3MEGT with RR of P3HT having 82 % 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 a substrate because of hydrophobic P3HT and hydrophilic P3MEGT. P3HT chains with lower surface tension were located at the air side, while P3MEGT chains were located at the substrate. Parallel oriented lamellar nanostructure induced end-on orientation of P3HT and P3MEGT chains, which significantly enhances the vertical hole mobility compared to P3HT continuous thin films with edge-on orientation (Figure 1).

End-on chain orientation of poly(3-hexylthiophene)-containing rod-rod diblock copolymer

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