Synthesis and Temperature-Responsive Properties of Novel Semi-interpenetrating Polymer Networks Consisting of a Poly(acrylamide) Polymer Network and Linear Poly(acrylic acid) Chains

A novel semi-interpenetrating polymer network (semi-IPN) gel consisting of an AAm gel and linear PAAc chains was designed and developed. The semi-IPN gel was simply prepared by infiltrating PAAc chains into AAm gel networks from an outer PAAc solution through immersion of AAm gels in the PAAc solution. The semi-IPN gel swelled at higher temperature and shrunk at lower temperature. Swelling-ratio transition temperatures of the semi-IPN gel shifted to lower values with increasing pH of the surrounding PAAc solution. The swelling-ratio transition of the semi-IPN gel became sharper with higher-molecular-weight PAAc. These swelling-ratio changes were completely reversible. A prototype of a light modulator was fabricated utilizing semi-IPN microgel particles containing 20 wt % of carbon black pigment. The transmittance of the light modulator was altered from 63 to 8% when the light modulator was heated from 10 to 60 °C.