Deposition of Thermoresponsive Plasma Polymer Films from N-Isopropylacrylamide Using Dielectric Barrier Discharge at Atmospheric Pressure

Abstract

Thermoresponsive polymers are of great interest as functional coatings in biomedical applications. Poly-N-isopropylacrylamide (NiPAAm) is a widely used compound that switches its surface properties from hydrophilic to hydrophobic by passing the lower critical solution temperature of 32°C. This study investigated plasma polymerization of NiPAAm (pp-NiPAAm) using a dielectric barrier discharge. The films’ chemical composition, thermoresponsive behavior, and stability in water were analyzed. Small effects with regard to thermoresponsive behavior were observed for films with high retention of the monomer structure. Unfortunately, however, these films were not stable in water, so plasma copolymerization was performed to improve film stability. Two different monomers were chosen: vinyltrimethoxysilane and glycidyl methacrylate. Thin films of pp-NiPAAM-co-glycidyl methacrylate show thermoresponsive behavior. While stability in water was improved significantly, the responsive behavior was lost after storing these films in water. Future work to ensure the long-term stability of pp-NiPAAm films, particularly in an aqueous environment, has to be done.