Chemical and electrochemical grafting of polythiophene onto polystyrene synthesized via 'living' anionic polymerization

Abstract

A novel strategy for chemical and electrochemical grafting of polythiophene onto a polystyrene backbone is reported. For this purpose, polystyrene was synthesized via 'living' anionic polymerization, and then brominated at the para position of the aromatic rings of the polystyrene (PSt-Br). The bromo groups of the PSt-Br were converted to thiophene groups using the Grignard reaction, and a thiophene-functionalized PSt macromonomer (ThPStM) was synthesized. The degree of thiophene functionalization was found to be approximately 9% from H-1 NMR spectroscopy. The resultant macromonomer was subsequently used in chemical and electrochemical copolymerization reactions with thiophene monomers to afford a polystyrene-graft-polythiophene (PSt-g-PTh) copolymer. The number average molecular weights of PSt, and chemically and electrochemically synthesized PSt-g-PTh graft copolymers were found to be 17 300, 29 700, and 25 600 g mol(-1), respectively, from gel permeation chromatography (GPC) analysis. The electroactivity behaviors of the synthesized samples were verified under cyclic voltammetric conditions, and their electrical conductivities were measured using the four-probe technique. The electrical conductivity and electroactivity measurements showed that the PSt-g-PTh graft copolymer has lower electrical conductivity and electroactivity than those of the pure PTh. However, these lower values can be improved at the price of solubility, and processability. Moreover, thermal behaviors of the synthesized polymers were investigated by means of differential scanning calorimetry and thermogravimetric analysis.