Multiple switching photochromic poly(N-isopropylacrylamide) with spironaphthoxazine hydrogel

Radical polymerization was used to synthesize a multiple switching photochromic poly(N-isopropylacrylamide) with spironaphthoxazine hydrogel (PNIPA–SPO), which undergoes thermally controlled, reversible switching from solution phase to gel phase at the lower critical solution temperature. The internal microstructure of the PNIPA–SPO hydrogel with a fibrous, three-dimensional structure was investigated by SEM. A complicated multiple switch in PNIPA–SPO hydrogel was realized by light, thermal and proton stimulation, which makes its application promising in the fields of opto- and electronic smart materials, logic gate, nanomachines, sensors and other molecular photonic devices.