Preparation and characterization of poly(4-alkyltriphenylamine) by chemical oxidative polymerization

High molecular weight poly(4-alkyltriphenylamine) was synthesized by chemical oxidation polymerization. 13C NMR spectra of the obtained polymers revealed that coupling reaction occurred exclusively at the para-position of unsubstituted N-phenyl rings. Poly(4-n-butyltriphenylamine) (P-nBTPA) showed better solubility and processability than polymers prepared from 4-methyltriphenylamine (MTPA) and 4-t-butyltriphenylamine (tBTPA) because of the high molecular weight and the flexible long n-butyl group in the side chain. Thus, P-nBTPA allows us to prepare the film from its solution in organic solvent with ease. The rigid structure of polymeric backbone affords high glass transition temperature of 182 °C, indicating high thermal stability. Extended conjugation over polymer chain results in red shift of UV absorption up to 375 nm and low ionization potential compared to monomer. The results of the ionization potential measurement and the redox behavior suggest that the polymer has great potential as a hole-transporting material (HTM). The drift mobility of P-nBTPA measured by a standard time-of-flight (TOF) method was found to be of the order of 10−5 cm2/(V s). The results of the photoconductivity measurement revealed that the photoconductivity of P-nBTPA showed much higher than that of poly(N-vinylcarbazole).