Synthesis, characterization, and photochromic behaviors of polythiophene derivatives in the solid state

Novel polythiophene derivatives with azobenzene chromophore side chains, poly[3-(6-((4-phenylazo)phenoxyl)hexyl)thienylacetate] (PATh-6), and the copolymers of 3-(6-((4-phenylazo)phenoxyl)hexyl)thienylacetate with 3-alkylthiophenes including 3-hexylthiophene and 3-dodecylthiophene (COP-66 and COP-612) were synthesized. The structure and the thermal property of these polythiophene derivatives were characterized by NMR, FT-IR, UV–vis, XRD, GPC, MDSC, and TGA. The differences in photochromic features and thermochromic behaviors between homopolymer and copolymers have been comparatively studied. The photochemical control of photoluminescence property was achieved with homopolymer PATh-6 both in solution and in the solid state. However, this photo-induced effect becomes less prominent for copolymers COP-66 and COP-612 due to the lower content of azobenzene chromophore in the side chain of copolymers. The photo-induced photochromic feature of homopolymer PATh-6 might be promising for the development of novel field-responsive materials.