Thermal and pH Sensitive Blends Formed by Chitosan and Poly(N-Vinylcaprolactam)

The development of smart polymeric films capable of responding to external and internal stimuli is of great interest in the biomedical and industrial fields for applications that require controlled drug release through pH variation, thermal stimuli, or both. This study aimed to develop and characterize polymeric blends composed by chitosan (CS) and poly(N-vinylcaprolactam) (PNVCL) with dual thermal and pH responsiveness. The films were prepared by solution casting using different CS/PNVCL ratios (90/10, 70/30, and 50/50) and characterized by ATR-FTIR, TGA, DSC, SEM, s-SNOM, contact angle, opacification, and swelling tests. FTIR and s-SNOM confirmed interaction and partial miscibility between the polymers. The films exhibited thermoresponsiveness, changing from transparent to opaque in temperatures from 25 °C to 32 °C, depending on composition. The pH responsiveness analysis indicated that the films demonstrated a greater increase in diameter (more than 80%), when subjected to acidic solution. The blend films presented Tg values of 72.38 °C, 140.41 °C, and 142.22 °C for the CS/PNVCL compositions 90/10, 30/70, and 50/50, respectively, intermediate to those observed for the pure precursor polymers (68.74 °C for CS and 182.39 °C for PNVCL). To the best of our knowledge, studies on solid polymeric systems responsive to pH and temperature, like those developed in this work, have not been performed.