Tetramethylbithiophene in π-conjugated alternating copolymers as an effective structural component for the formation of spherical assemblies

Abstract

π-Conjugated alternating copolymers containing a tetramethylbithiophene unit show a strong tendency to form well-defined, sub- to several-micrometer-sized spheres. The twisted bithiophene unit inhibits interchain stacking and anisotropic crystal growth of these copolymers, leading to the formation of structurally isotropic spheres by means of a slow diffusion of a nonsolvent into a solution of the copolymers. These micrometer-sized spheres display extremely long photocarrier lifetimes (∼10⁻³ s) in comparison with cast films from the solutions of the polymers and those of the irregular aggregates (<10⁻⁶ s).