The influence of an in situ-grown, sol --> gel-derived silicon oxide filler on mechanical, gas permeation and solvent affinity properties of Surlyn(R) materials, and melt processibility of Surlyn(R)/[silicon oxide] hybrid resin, was studied. Tensile modulus increases while elongation-at-break decreases with increasing silicon oxide uptake. He gas permeation vs. pressure profiles imply dual mode sorption. Swelling in n-hexane, 1-PrOH and xylene decreases as silicon oxide loading increases, the highest uptake being that of xylene. [Surlyn(R)Zn+2]/[silicon oxide] has better solvent resistance than the H-form hybrid for each solvent. Affinity of the Zn-form hybrid for xylene is considerably greater than that for 1-PrOH and n-hexane. Melt flow index of the filled H-form is lower than that of the unfilled H-form but higher than that of the partially Zn neutralized unfilled form. FTIR analysis of hybrids previously subjected to the melt flow index experiment shows that the silicon oxide phase remained intact but that the high temperatures drove condensation reactions between SiOH groups. After in situ sol-gel reactions and drying [Surlyn(R)-H]/[silicon oxide] flakes were passed through an extruder to assess the effect on silicon oxide structure of melt-processing conditions. All silicon oxide IR fingerprint bands for the processed hybrid persist, the spectrum closely resembling that of a nonextruded hybrid including the signature of Si-OH groups. Si-29 solid-state NMR spectroscopy was used to probe degree of molecular connectivity within the silicon oxide phase. The spectrum is consistent with those of nonextruded hybrids in that Si atom coordination around SiO4 units is predominantly Q(3) and Q(4), the bias in the distribution toward Q(3) being in harmony with the IR results.