Shrinking Behavior of Surfactant-Grafted Thermosensitive Gels and the Mechanism of Rapid Shrinking

Surfactant-grafted hydrogels with a fast response to temperature were prepared. In order to clarify the mechanism of rapid shrinking, the effects of the grafted surfactant and the homogeneity of the main chain were investigated. Poly(NIPAAm-co-S180A) gels prepared using a chemical cross-linker (bis-PNS gels) exhibited rapid shrinking, as did PNS gels prepared by γ-ray irradiation (y-PNS gels). This suggested that the rapid shrinking of the PNS gel did not depend on the homogeneity of the main-chain structure. The shrinking kinetics of the bis-PNS gels depended on the amount of the introduced surfactant, which means that shrinking is enhanced by micelle formation as a dynamic driving force. From the analysis by dynamic light scattering (DLS) and scanning microscopic light scattering (SMILS), it was suggested that the micelle structure, which induced rapid shrinking, existed in the bis-PNS gel.