Behavior to UV irradiation of the polyurethanes containing azobenzene side groups in the main chains structure

The present study investigates new polyurethanes with improved stability to UV radiation by the inclusion of azobenzene side groups on the polymer main chain. These polyurethanes were prepared from a prepolymer (polycaprolactone diol and 1,6-hexamethylene diisocyanate) with 2,4-dihydroxyazobenzene (Sudan Orange G) as a chain extender. A polyurethane chain-extended with 1,4-butanediol was prepared for comparison. The paper studies how the amount and structure of the chain extenders affect the polymer structure and the mechanical, surface and thermal properties of the obtained polyurethanes, before and after subjection to UV irradiation, All the synthesized polyurethanes showed good thermal stability up to 250 oC. In terms of mechanical properties, the samples exhibit good tensile strength and elongation at break. The surface contact angle increases with chain extender content and UV exposure time. The inclusion of azobenzene groups into the polyurethane main chain makes these polyurethanes appropriate for use in colored polymer materials with good UV radiation stability.