Gas transport properties of reverse selective nanocomposite materials

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Title: Gas transport properties of reverse selective nanocomposite materials
Author: Matteucci, Scott Tyson, 1976-
Abstract: The effect of dispersing discreet periclase (magnesium oxide ) or brookite (titanium oxide ) nanoparticles into poly (1 -trimethylsilyl -1 -propyne ) (i .e . , a super glassy polymer ) and 1 ,2 -polybutadiene (i .e . , a rubbery polymer ) has been examined . Particle dispersion has been investigated using atomic force microscopy and transmission electron microscopy to determine particle /aggregate size and distribution . Titanium dioxide nanoparticles dispersed into aggregates on the order of nanometers , as did magnesium oxide in 1 ,2 -polybutadiene . However , the magnesium oxide filled poly (1 -trimethylsilyl -1 -propyne ) did not exhibit nanoparticle aggregates below approximately one micron in characteristic dimensions . Nanocomposite transport properties were studied , where permeability and solubility coefficients were determined for light gases with increasing pressure , and diffusion coefficients were calculated from the solution -diffusion model . The permeability of light gases in the heterogeneous films increased with increasing particle loading . Depending on particle loading , brookite filled nanocomposite light gas permeability increased to over four times that of the unfilled polymer , whereas at high periclase loadings the nanocomposites exhibited light gas permeabilities in excess of an order of magnitude higher than the unfilled materials . Even at these high loadings the light gas selectivities were higher than predicted for films containing transmembrane defects . Solubility was relatively unaffected by the void volume concentration , although it did increase to some extent depending on the nanoparticle concentration . Wide angle X -ray diffraction , nuclear magnetic resonance , and Fourier transform infra -red experiments were used to determine if the nanoparticles remained stable during film preparation . TiO₂ nanoparticles did not appear to react with water , the polymer matrixes or test gases used in this research . However , under certain circumstances , periclase reacted with adventitious water to form brucite . A desilylation reaction occurred when brucite was exposed to polymers or small molecule compounds that contained a trimethylsilyl group attached to a conjugated organic backbone . This reaction caused certain disubstituted polyacetylenes to become insoluble in common organic solvents .
URI: http : / /hdl .handle .net /2152 /3631
Date: 2008-08-29

Citation

Gas transport properties of reverse selective nanocomposite materials. Doctoral dissertation, The University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /3631 .

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