| Hybrid organic-inorganic composites have been synthesized by the sol-gel processing of triethoxysilane end functionalized poly(tetramethylene oxide) and tetraethxoysilane. The resulting transparent materials are elastomeric gels crosslinked by an amorphous polysilicate phase. Elementary rubber-elasticity theory in conjunction with dynamic mechanical spectroscopy was applied to these seemingly nonideal networks to quantify the change in phase interaction induced by aging the benchmark acid catalyzed gels in a basic solution of 70% ethylamine in water. The change in the average molar mass between crosslinks explained the previously published mechanical and dynamic mechanical results. Furthermore, the application of this theory to these seemingly nonideal networks resulted in network parameters that were in excellent agreement with traditional equilibrium swelling estimates.; The work was then extended by utilizing this ethylamine solution to catalyze the sol-gel reaction in-situ. The effect of this change in catalyst upon the oxygen diffisivity of the hybrids as a function of polysilicate loading was investigated using a luminescence based approach. While the diffusivity of the acid catalyzed gels decreased with increasing loading, the base catalyzed gels did not indicating that the polysilicate domains resulting from the base catalysis possess considerable porosity. However, the pores appear to be much too small for Knudsen diffusion, a commonly observed gas separation mechanism in porous ceramic membranes.; To investigate the influence of polysilicate network polarity and spatial distribution, the sol-gel processing of the hybrids was adjusted to produce two classes of gels. One exhibited a more discrete polysilicate phase possessing greater network connectivity and reduced silanol content than the other. This was accomplished by using dimethylformamide in place of tetrahydrofuran as the organic solvent constituent of the sol. Poly(methacrylic acid)-PTMO-polysilicate semi-interpenetrating polymer networks (SIPNs) were then produced by {dollar}gamma{dollar} polymerizing monomer swollen hybrids using a {dollar}sp{lcub}60{rcub}{dollar}Co source. Fourier transform infrared spectroscopy was used to confirm the reduced silanol content. Tensile testing revealed that the better developed, less polar inorganic network containing SIPNs exhibit decreased elongation at failure and post-yield elongation to strain hardening. Thus, the origin of the exceptionally high elongation of these SIPNs is a diffuse polysilicate network capable of extensive hydrogen bonding and deformation under load. |
