Thermoresponsive blends formed by poly(<i>N</i>‐vinylcaprolactam) and thermoplastic polyurethane

Abstract Poly( N ‐vinylcaprolactam) (PNVCL) is a thermoresponsive polymer, which presents a transition from hydrophilic to hydrophobic behavior close to the physiological temperature, being promising for biomedical applications. However, the production of finished products with PNVCL is difficult due to its high mechanical fragility in the solid state. In the present work, in order to prepare a thermoresponsive film with good mechanical properties, a blend of PNVCL with thermoplastic polyurethane (TPU) was prepared. Three compositions of PNVCL/TPU were studied with mass proportions of 90/10, 70/30, and 50/50, respectively. The films were flexible, miscible and presented different thermoresponsive behaviors, with changing from transparent to opaque varying from 31 to 40°C. Contact angle analysis showed significant changes in the hydrophilicity of the films' surfaces with temperature variation. Moreover, it was possible to induce a change in solid films from transparent to opaque by varying the temperature and verify the reversibility of this change. In addition, tensile tests were carried out, which proved, for PNVCL/TPU blends, the reduction of film brittleness with TPU increase. To the best of our knowledge, it is the first work that presents thermoresponsive properties of solid films formed by a blend of PNVCL and TPU.