Teardrop-Shaped Hollow Polystyrene Nanoparticles for Improving the Mechanical and Thermal Properties of Polyvinyl Alcohol-Based Syntactic Foam Films

The application of polyvinyl alcohol (PVA) films is still restricted due to their poor hydrophilicity, mechanical strength, and thermal stability. To improve these properties, a teardrop-shaped hollow polystyrene (HPS) nanoparticle was prepared in this work and further applied as the reinforcing nanomaterial. Herein, a teardrop-shaped silica nanoparticle was first used as the hard template; polystyrene was in situ-synthesized on the surface of teardrop-shaped silica, followed by the etching of the silica template. By tuning the synthesis parameters (e.g., styrene concentration and etching time), the optimal structure of HPS was obtained; subsequently, HPS was mixed with PVA by a solution-mixing method, which in turn produced the PVA-based synthetic foam film. Using optimal synthesis parameters of HPS and its loadings, the obtained syntactic foam films exhibited high transparency, excellent mechanical strength and toughness, and good thermal stability. Compared to pure PVA film, the tensile strength and toughness of PVA-based syntactic foam films containing 1.0 wt % HPS were improved by about 55 and 77%, respectively; the glass transition temperature and onset decomposition temperature of PVA-based syntactic foam films increased to about 32 and 66 °C, respectively. The research exemplifies the great promise of HPS toward practical application in polymer syntactic foams.