Spherical assemblies formed from π-conjugated alternating copolymers having fluorene and thiophene components

Self-assembly of conducting polymers were comprehensively studied by means of slow precipitation from polymer solutions upon addition of a vapor of nonsolvents. Polymers such as polyfluorene and polythiophene hardly formed defined and discrete objects but only gave ill-defined aggregates. In contrast, some alternating copolymers having both fluorene and thiophene components in their repeating unit self-assembled into well-shaped spheres with sub-micrometer to several micrometer in the diameters. The differences in the assembling geometries derive from the crystallinity of the polymers, where the copolymers possess large steric hindrance on their backbone that reduces planarity of the polymers and inhibits anisotropic crystal growth. Changing the assembling parameters can systematically control diameter and deviation of the spheres.