Preparation and Characterization of Light-Shielding Gel Sheet Using Thermoresponsive Polymer

Abstract

This study aims to develop a new light-shielding gel sheet, which can change its transparency and opaqueness reversibly in response to temperature with little volume change, composed of poly N-isopropyl acrylamide （PNIPAM）, which is a temperature responsive polymer with a lower critical solution temperature（LCST）of 32°C, and agar. For this purpose, the influence of PNIPAM concentration（0.6-6 wt%）and agar concentration（0.6-3 wt%）on the transmittance of visible and near infrared light and volume shrinkage ratio of PNIPAM gel sheet during heating and cooling were investigated. Furthermore, the structural change of PNIPAM gel sheet with temperature change was discussed from these results. The transmittance of PNIPAM gel sheet increased at 25°C（below LCST）and decreased at 50°C（above LCST）with the increase of PNIPAM concentration and the decrease of agar concentration. In addition, the volume shrinkage ratio of PNIPAM gel sheet by heating decreased when the agar concentration increased. These results reveal that the PNIPAM gel sheet prepared with 6 wt% of PNIPAM and 2 wt% of agar has the highest performance.