Improvement of the water resistance of atactic poly(vinyl alcohol) nanowebs by a heat treatment

Nanoscale materials can be rationally designed to exhibit significantly changed physical, chemical, and biological properties because of the extremely small dimensions. Therefore, atactic poly(vinyl alcohol) (a‐PVA) nanowebs by an electrospinning technique have very high water solubility because of their nanoscale in comparison with microscale materials such as fibers and films. In this study, a‐PVA nanowebs were prepared via electrospinning under suitable conditions to form PVA webs with uniform nanofibers (fiber average diameter = 200 ± 50 nm), not a bead or bead‐and‐string morphology. Furthermore, to improve the water resistance of the water‐soluble a‐PVA nanowebs, the PVA nanowebs were heat‐treated at various heat‐treatment temperatures. The melting temperature of the heat‐treated PVA nanowebs shifted toward a lower temperature with an increase in the heat‐treatment temperature, and this indicated that micronetwork domains formed. Moreover, with the exception of a PVA nanoweb treated at an excessive heat‐treatment temperature, the heat‐treated PVA nanowebs showed higher crystalline and mechanical properties than a pure PVA nanoweb.