Gas permeation in poly(ether imide) nanocomposite membranes based on surface-treated silica. Part 2: With chemical coupling to matrix

Nanocomposite membranes based on nano-sized SiO₂ particles with chemical coupling to the polymer matrix are described with special emphasis on gas permeation properties. In this paper, poly(ether imide) with reactive imide rings in the backbone was used as the matrix to which the SiO₂ particles were chemically bonded via an amine-containing silane coupling agent. Four types of nanocomposite membranes were prepared by solution casting and melt processing and characterized in terms of morphology and void volume formed due to adding SiO₂ particles. The relative gas permeability of the nanocomposite with chemical coupling to matrix was decreased by the presence of SiO₂ particles. Diffusion coefficients computed from time lag data also decreased with SiO₂ content. However, solubility coefficients computed by dividing the experimental permeability by the diffusivity obtained from the observed time lag increased with SiO₂ content contrary to simple composite theory. These permeation properties are discussed in terms of the void volume fraction estimated by density observations. In addition, TEM and SEM were used to explore the morphology of these nanocomposite membranes.