Hyperbranched Azo-Polymers Synthesized by Azo-Coupling Reaction of an AB2 Monomer and Postpolymerization Modification

Abstract

A series of hyperbranched azo-polymers have been synthesized by two-stage azo-coupling reactions, in which a hyperbranched precursor azo-polymer (HPAP) was prepared by step-growth polymerization of an AB2 monomer through azo-coupling reaction and then was further modified by postpolymerization azo-coupling reaction at the peripheral groups. The AB2 monomer, di[2-(N-ethylanilino)ethyl]-5-aminoisophthalate, was synthesized from the nucleophilic substitution reaction between N-ethyl-N-(2-chloroethyl)aniline and 3,5-bis(carboxyl)aniline. On the basis of the monomer, HPAP was prepared by step-growth polycondensation of the diazonium salt of the AB2 monomer. The hyperbranched precursor polymer was then reacted with diazonium salts of 4-nitroaniline, 4-aminobenzoic acid, and 4-aminobenzonitrile to introduce different types of donor−acceptor azo-chromophores at the peripheral positions. The structure and properties of the azo-polymers were characterized by the spectroscopic methods and thermal analysis. The hyper...