Synthesis and characterization of highly fluorescent polythiophene derivatives containing polystyrene sidearms

In this study, macroinitiators with different content of atom-transfer radical polymerization (ATRP) functional group on polythiophene backbone were first prepared by the copolymerization of 3-[1-ethyl-2-(2-bromopropionate)]thiophene and 3-hexylthiophene with various feed ratio. Then poly [3-hexyl-2,5-thienylene-co-3-[1-ethyl-2-(2-[poly(styrene)lpropionate)]-2,5-thienylene] (PTTBr-PS) with different graft density were obtained by ATRP of styrene from these macroinitiators in anisole. The degree of polymerization of PS sidearm (DPPS) was controlled by polymerization time. The structures of obtained graft copolymers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (H-1 NMR) and differential scanning calorimetry (DSC). Introduction of the PS sidearms onto the backbone of polythiophene was an attempt to trap the polythiophene backbone in a "solution-like" conformation, thus inhibit the packing of polythiophene backbone and result in the improvement of fluorescent property in solid state. This was verified by the UV-vis and fluorescence analyses. Besides, it was also found that the optical property of PTTBr-PS graft copolymer was dominated by its graft density and independent on the degree of polymerization of its PS sidearm. (C) 2007 Wiley Periodicals, Inc.