Preparation and properties of poly(vinyl alcohol)/vinyltrimethoxysilane (PVA/VTMS) hybrid films with enhanced thermal stability and oxygen barrier properties

To enhance the thermal stability and barrier properties of pure poly(vinyl alcohol) (PVA), a series of poly(vinyl alcohol)/vinyltrimethoxysilane (PVA/VTMS) hybrid films were prepared via a sol-gel process, and their physical properties were investigated as a function of VTMS content. During the sol-gel process, simultaneous reactions between hydroxyl groups of PVA and silanol groups of hydrolyzed VTMS and self-condensation of VTMS occurred, inducing a cross-linked network structure and greatly enhanced thermal stability and oxygen barrier properties. The glass transition temperature and thermal decomposition temperature (T_5%) of the PVA/VTMS hybrid films increased from 72.6 to 84.3 °C and 273.6 to 342.2 °C, respectively, with increasing VTMS content from 0 to 20%. Oxygen transmission rates of the hybrid films decreased from 6.12 to 0.17 cm³/m²×day, and those of the hybrid films incorporating 5%, 10%, and 20% VTMS were suppressed by 65.7%, 95.6%, and 97.2%, respectively, versus a pure PVA film. These are dependent on the chemical structure and morphology of the films with differing initial amounts of VTMS. The chemical affinity for water, intermolecular packing, and rigidity in polymer chains increased with increasing cross-linking by VTMS, leading to enhanced oxygen barrier properties and thermal stability in the PVA/VTMS hybrid films.

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