Showing papers by "Kenneth A. Mauritz published in 1990"

Microstructural evolution of a silicon oxide phase in a perfluorosulfonic acid ionomer by an in situ sol-gel reaction. 3. Thermal analysis studies

Abstract: Microcomposite membranes were produced via the in situ diffusion-controlled, acid-catalyzed sol-gel reaction for tetraethoxysilane in prehydrated and methanol-swollen Nafion perfluorosulfonic acid films. The thermal behavior of these microcomposites was investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found by TGA that significant

A general free volume-based theory for the diffusion of large molecules in amorphous polymers above the glass temperature. I. Application to di-n-alkyl phthalates in PVC

Abstract: The standard free volume theory has been extended to include the fundamental motions of large molecules. In addition to accounting for liberated penetrant translational entropy, a new feature consisting of an elementary displacement of the molecule that is but a fraction of its long dimension is introduced. An effective diffusion coefficient is derived for elongated molecules which is the result of averaging over probable penetrant jumps from zero up to the entire molecular length

Novel poly(n-butyl methacrylate)/titanium oxide alloys produced by te sol–gel process for titanium alkoxides

Abstract: A method has been developed to cast novel organic/inorganic hybrid films from multicomponent solutions containing titanium alkoxides, poly(n-butyl methacrylate), water, and isopropanol of prescribed compositions. The sol–gel reactions and controlled drying procedure yielded materials of mechanical integrity for which the multistep thermal degradation profile of the organic polymer has been significantly modified. A crystallization exotherm, presumably due to anatase formation, is seen for tetraethyl titanate-derived films beyond the organic degradation temperature. The trend of mechanical tensile parameters with increasing Ti oxide content depicts progressive material strengthening. FT-IR as well as the thermal and mechanical studies of these films suggest a highly unconnected and heterogeneous Ti oxide phase.

Microstructural evolution of a silicon oxide phase in a perfluorosulfonic acid ionomer by an in situ sol-gel reaction. 2. Dielectric relaxation studies

Abstract: Etude en fonction de la temperature et de la teneur en oxyde de silicium de la constante dielectrique complexe de membranes microcomposites preparees par la reaction sol-gel de Si(OEt) 4 dans une membrane Nafion prehydratee et gonflee par le methanol. Discussion des resultats sur la base des mecanismes de saut de charge dans un materiau a separation de microphase polaire/non polaire

A General Free Volume Based Theory for the Diffusion of Large Molecules in Amorphous Polymers Above Tg .2. Molecular Shape Dependence

Abstract: The theory of Mauritz and Storey has been generalized in this work to include large molecules of any shape. The basic improvement to the original restrictive model was affected by considering the elementary penetrant diffusive hopping vector to be the vector sum of component displacements along the instantaneous directions of the three principal axes passing through the molecular center of mass. The theory predicts that, for a fixed penetrant molecular volume, compacted structures migrate slower than corresponding extended structures