Preparation and characterization of novel main-chain azobenzene polymers via step-growth polymerization based on click chemistry

A novel α-azide and ω-alkyne A–B type azobenzene monomer, 3′-ethynylphenyl[4-(4-azidobutoxy)phenyl]azobenzene (EAPA), was synthesized and used to generate a novel polymer via step-growth polymerization using 1,3-dipolar cycloaddition reaction under the catalysis of CuSO4·5H2O/sodium ascorbate/H2O (“Click” chemistry). The structure of the resultant main-chain azobenzene polymer, PEAPA, was characterized by GPC, 13C NMR, UV–vis and FT-IR spectra. Thermal stability and crystallinity of PEAPA powder were studied by TGA and WAXD. The photo-induced trans–cis isomerization of PEAPA and EAPA in N,N′-dimethyl formamide (DMF) solution was investigated. Furthermore, the thermal cis–trans isomerizations of PEAPA and EAPA were also observed at 60 °C in dark. Thermal stability and trans–cis–trans isomerization behavior of PEAPA was compared with its non-triazole analog, PDHA.