Stimuli-Responsive and Mechanically-Switchable Electrospun Composites

We report on a family of electrospun nanocomposites, which are capable of altering their stiffness upon hydration. An electrospun mat of poly(vinyl alcohol) (PVA) was incorporated as the filler in a polymeric matrix consisting of either poly(vinyl acetate) (PVAc) or ethylene oxide–epicholorohydrin copolymer (EO–EPI). The tensile modulus of the EO–EPI-based composites was found to increase significantly upon incorporation of the PVA filler mat, while PVAc-based composites exhibited modulus enhancement only above the matrix glass transition. Materials based on the PVAc matrix and PVA electrospun filler exhibited a reversible reduction of the tensile modulus by a factor of 280 upon exposure to water. In contrast, composites comprised of a rubbery EO–EPI matrix and PVA filler showed a reduction of tensile modulus upon water uptake, but with incomplete restoration when dried. A systematic investigation revealed that the underlying mechanism of mechanical response is related to the matrix–filler interactions and filler crystallinity. The robust technique of electrospinning allows the tailoring of matrix–filler interactions in a new series of all-organic composites to achieve desired mechanical response upon exposure to various stimuli.