Synthesis of charge transporting polymer containing TPD units using Friedel–Crafts reaction

N,N′-bis(4-alkylphenyl)-N,N′-diphenylbenzidine (alkyl-TPD) was reacted with 1,4-bischloromethylbenzene, 9,10-bischloromethylanthracene (BCA), 4,4′-bis(chloromethyl)-1,1′-biphenyl (BCP) or 2,7-bis(bromomethyl)-9,9-di-n-butylfluorene (BBF) by condensation polymerization using Friedel–Crafts reaction. The polymers were obtained in high yield and high molecular weight. TPD having two methyl substituents showed higher reactivity and larger gel content than one having two butyl substituents. The structure of polymers was determined by 1H NMR spectroscopy. It was found that all polymers showing two methylene signals arises from benzyl proton, which indicates that the polymerization occurred not only at the para-position of phenyl group but also at the meta-position of alkylphenyl group in TPD derivatives. All polymers had almost the same oxidation potential as that of TPD itself. The polymer containing anthracene unit showed not only oxidation but also reduction peak.