Photo-responsive systems based on anisotropic composites of poly(N-vinyl formamide) and active fillers using directional freezing combined with gamma irradiation crosslinking

Abstract

This study deals with the fabrication of smart anisotropic composite systems capable of reacting to light stimulus and reversibly providing significant change in the length. Surface-modified carbon nanotubes (CNTs) and poly(pyrrole) (PPy) nanotubes were used as photoactive fillers. Anisotropic composites containing these fillers and poly(N-vinyl formamide) (PNVF) matrix were fabricated using a directional freezing technique with freezable monomer, N-vinyl formamide (NVF), as structure guiding medium and subsequent gamma irradiation polymerization and crosslinking technique. The dielectric properties showed that there is the presence of both relaxation processes α and β, which are significantly influenced by the presence of photoactive filler. The anisotropic distribution of fillers in samples was confirmed using microscopical, electrical conductivity and mechanical properties analysis. Finally, the photoactuation capabilities were investigated and showed enhanced photoactive response for the anisotropic system in the change in the length up to 54 μm after irradiation at 627 nm with a very low light intensity of 6 mW cm⁻² in a fully reversible and repeatable manner. The simple, affordable, and industrially scalable fabrication technique opens an avenue for smart anisotropic photoactive composite systems.