Thermal-induced Phase Transition Hydrogel Revealed with Photonic Crystal
Abstract
In this study, a poly(vinyl alcohol) (PVA) based thermo-sensitive polymer was prepared by cationic and acetalization of PVA (CAPVA), which showed the lowest critical solution temperature (LCST). The polymer is characterized by the fact that below LCST, the CAPVA hydrogel is transparent; when the temperature is higher than LCST, CAPVA becomes precipitated and turbid. The advancement of this study is that by combining the thermosensitive polymer CAPVA with a photonic crystal (PC) having the optical property of structural color, the phase change phenomenon of thermally induced CAPVA can be observed with the naked eye. Then, the CAPVA was combined with photonic crystal (PC) to reveal the thermally induced phase transition phenomenons rely on the structural color rendering of PC. Fourier transform infrared (FTIR) spectroscopy and UV spectrophotometer were utilized to characterize the structure and LCST of CAPVA. Optical-fiber spectrometer was utilized to capture the diffraction properties of PC and CAPVA/PC. The results showed that the CAPVA/PC combined hydrogel can visually detect the temperature change, which further provides ideas for the design of thermo-switch, controlled drug release and temperature sensor materials.