Modulating the Thermal and Light Responsive Behavior of Spirobenzopyran-Based Poly(N-isopropylacrylamide) Hydrogels

Spirobenzopyrans are an interesting class of compounds which have recently attracted significant attention in the field of “smart” material development, owing to their diverse stimuli behavior, e.g. light, temperature, stress and pH. However, the functionality of such material alone is often limited, and thus the integration of these with other functional polymers is desired. Here we demonstrate the capability of synthesizing light and temperature responsive spirobenzopyran-functionalized poly(N-isopropylacrylamide) (PNIPAAm) hydrogels. To improve the light responsive behavior and broaden the spectra of light absorbed by the hydrogel, particularly pertaining to the visible range, different derivatives of sprirobenzopyran were integrated in the hydrogel along with a pore forming agent. The thermoresponsive behavior of these hydrogels was studied with differential scanning calorimetry and then compared to traditional PNIPAAm hydrogels. The effect of surfactants and solvents on the transition temperature of such hydrogels was also investigated. The integration of such multi-functional compounds in hydrogels could have interesting implications for the development of novel “smart” devices.