Synthesis and characterization of P(AAm-co-AAAB) photoresponsive copolymer and hydrogels

Abstract

The synthesis and characterization of a novel copolymer Poly(acryl amide-co-acrylamido azobenzene) (P(AAm-co-AAAB)) and its hydrohydrogels consisting of acrylamide (AAm), acrylamido-azobenzene (AAAB) with a photo-responsive azobenzene chromophore, were reported in this article. The copolymerization was carried out with a free-radical polymerization route using 2,2-azobisisobutyronitrile (AIBN) as an initiator, tetrahydrofuran (THF) as a solvent and N,N-methylene bisacrylamide (MBAA) as a crosslinking agent for hydrogel. The structures of P(AAm-co-AAAB) were charactered by Fourier transform infrared spectroscopy (FT-IR) and 1 H-NMR spectroscopy, and their photo-responsive behaviors was studied. The spectra of P(AAm-co-AAAB) copolymer solution irradiated with UV light showed one strong intensity peak at about 342 nm, and with the irradiation time increased, the intensity of the absorption decreased. The hydrogels also showed good photoresponses. With the UV irradiation time increased, the volume of the hydrogels decreased gradually. The photoresponsive behaviors was reversible, without the irradiation, the volume of the hydrohydrogels increased to the original state. This photoresponsive behavior was caused by the cis-trans isomerism of azobenzide in the chains of their structures.

Photoresponsive Properties of a Azobenzene-Based Polyacrylamide Copolymer

“…All other reagents, including acryloyl chloride, p-aminoazobenzene, triethylamine, benzene, hydroquinone and tetrahydrofuran, were all analytical-grade and made in China, they were used without further purification. The AAAB monomer contains azobenzene groups was synthesized by a method described elsewhere [2,3].…”

“…Synthesis of p(AAm-co-AAAB) copolymer. The copolymer of AAm and AAAB was synthesized in THF via a free-radical polymerization route initiated by AIBN [2,3] .…”

“…Azobenzene and its derivatives are interesting materials due to their environmental stability, processing facility, and superior photosensitive behavior. Azobenzene species undergo isomerization from the stable trans form to the metastable cis isomer when expose to UV light, and the trans form is readily recovered by removing the irradiation [2][3][4][5][6][7][8][9]. For preparing azobenzene-based polymers, it is important to explore methods for incorporating azobenzene groups onto the backbone of the macromolecule.…”