Structure and water permeability and resistance characteristics of N-isopropylacrylamide-based polymer/polyurethane resin films

In this study, moisture-permeable waterproof film materials exhibiting temperature-sensitive hydrophilicity are investigated. The water resistance properties of copolymer films prepared by combining water-soluble poly(N-isopropylacrylamide) (poly-NIPAM) with hydrophilic polyurethane (PU) are examined. Water-soluble poly-NIPAM is synthesized as a diol and then copolymerized with PU. Structural investigations confirm that water-soluble poly-NIPAM and hydrophilic PU are combined through PU links. In terms of physical properties, the films are confirmed to be water-insoluble. Furthermore, based on the relationship between the water-swelling ratio of the film and the water temperature, the films exhibit temperature-sensitive hydrophilicity, with the water-swelling ratio changing across the lower critical solution temperature (LCST). Moreover, the drying rate of the water-absorbing film is different across the LCST. From these results, it is confirmed that a functional film with temperature-dependent hydrophilicity is achieved. This property enables the poly-NIPAM/PU copolymerized films to be used as moisture-permeable waterproof fabrics for sportswear.