Polythiophene Diblock Copolymer with Different Solvent Affinities of the Side-Chain Substituents: Solvatochromism and Effect on the Electronic Conjugation

A new diblock copolymer composed of a regioregular block of poly[3-[2-(2-methoxyethoxy)ethoxy]methylthiophene], bearing as side-chain a hydrophilic substituent, and a regioregular block of poly[3-(1-octyloxy)thiophene], is prepared and characterized. The properties are compared with those of a related copolymer composed of poly(3-hexylthiophene) and poly(3-alkoxythiophene) blocks. The solvatochromic properties of these materials in solution are investigated by absorption and emission spectroscopy upon gradual addition of a poor solvent, and compared with those of the parent regioregular homopolymers. The experimental results are interpreted in terms of electronic interactions between the blocks. It is found that the different hydrophilicity of the side chain plays a crucial role for the electronic communication between blocks in poly(3-alkylthiophene)-block-poly(3-alkoxythiophene) copolymers.