Chemical networks of poly(vinyl alcohol)-Si hybrid films and the thermodynamics of their interaction with water

Abstract

Organic-inorganic hybrid polymer films are prepared through the sol-gel method via the hydro lytic condensation of tetraethoxysilane in a 4% aqueous solution of poly(vinyl alcohol). The films are polymer networks containing O-Si-O bonds between chains formed via the interaction of OH groups of alcohol and Si-OH groups of the products of hydrolysis of tetraethoxysilane. The films contain 10.8-26.2 wt % Si in the polymer matrix. Isotherms of water vapor sorption by the films are determined and used to calculate the molecular mass of polymer chain fragments between crosslink junction points in terms of the Flory-Rehner theory. For hybrid polymer networks, the products of sol-gel synthesis, this calculation is performed for the first time. The molecular mass of chain fragments between crosslink junction points decreases from 9000 to 180 with an increase in the content of Si in the films. Poly(vinyl alcohol)-Si hybrid films are active during the separation of components of organic-aqueous media (a solution of tetrahydrofuran in water). The selectivity of the films increases as the molecular mass of chain fragments between crosslink junction points decreases, that is, as the density of the chemical network increases.