Dual-responsive cellulose fabric based on reversible acidichromic and photoisomeric polymeric dye containing pendant azobenzene

An acid and UV dual-responsive cellulose fabric was developed via coating with a polymeric dye based on waterborne polyurethane and azobenzene chromophore to provide additional smart characteristics for textiles. The incorporation of azobenzene chromophore into polyurethane chain through chemical bonding enhanced the thermal stability. The maximum absorption peak of the polymeric dye and its coated fabric shifted from 410 nm to 520 nm upon pH decreasing from 6 to 1, accompanying with pronounced color change from yellow to amaranth due to structural transition from diazo to hydrazone form. The acidichromic property of the polymeric dye also presents an outstanding repetition stability. The trans -isomers in the polymeric dye transformed into cis -isomers rapidly (1 s) in response to UV irradiation, while its recovery was much slower (6 h) in dark due to the large molecular and volume of polyurethane chains. Upon trans-cis isomerism, the coated fabric presented slight color change between yellow and orange after alternative UV irradiation and dark. The stimuli-responsive cellulose fabric with reversible acidichromic and photoisomeric properties can be a promising candidate for developing a wearable and flexible sensor to monitor environmental changes.