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A study is conducted to show that a new sol-gel precursor consists of positively charged polyhedral cubelike silsesquioxanes. The result reveals that over the course of condensation of sols, the refractive index of the modes attributed to the polysilsesquioxanes species exhibited strong dispersion, which led to a shift of the vibrational band position in the experimental ATR spectra.

Bis[(ureapropyl)triethoxysilane] bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU), an organic-inorganic hybrid, diluted in either EtOH or a mixture of EtOH-PrOH, was used in thin film form (<200 nm) to inhibit the corrosion of AA 2024 alloy. Potentiodynamic, time-dependent cyclovoltammetric measurements and salt spray tests showed that the corrosion inhibition of the latter was 10 times higher than that of the former films. This was correlated with the higher degree of hydrolysis and the formation of more open polyhedral silsesquioxane species (T2) in the bulk heat-treated PDMSU/EtOH-PrOH xerogels (29Si NMR spectra). The structure of the coatings deposited on AA 2024 Al alloy was deduced from the infrared reflection-absorption (IR RA) spectra, which revealed more extensive urea-urea interactions and more efficient silane-Al interface bonding for the PDMSU/EtOH-PrOH coatings with higher corrosion inhibition. Ex situ IR RA potentiodynamic spectroelectrochemical measurements of PDMSU coatings revealed that their degradation did not proceed via the formation of silanol groups and consequent hydration of the coatings but that they decomposed above E(corr) by forming fragments composed of -CH2- segments in an all-trans conformation.

A new sol-gel precursor, based on 1-methyl-3-[3-(trimethoxy-lambda(4)-silyl)propyl]imidazolium iodide (MTMSPI(+)I(-)), was synthesized and investigated as a potential novel quasi-solid-state ionic liquid redox electrolyte for dye-sensitized photoelectrochemical (DSPEC) cells of the Graetzel type. MTMSPI(+)I(-) was hydrolyzed with acidified water, and the reaction products of the sol-gel condensation reactions were assessed with the help of (29)Si NMR and infrared spectroscopic techniques. Results of time-dependent analyses showed the formation of a positively charged polyhedral cubelike silsesquioxane species, which still contained a small amount of silanol end groups that were removed after heating at 200 degrees C. After cooling, the material formed was a tough, yellowish, and transparent solid, consisting mainly of ladderlike polysilsesquioxane species. The specific conductivity (sigma) of the nonhydrolyzed MTMSPI(+)I(-) (no I(2)) was 0.23 mS/cm, while the activation energy (E(a)), determined from the Vogel-Tamman-Fulcher (VTF) relation, was 0.29 kJ/mol. After 56 days of aging the sigma value of the hydrolyzed MTMSPI(+)I(-) dropped to 0.11 mS/cm but the viscosity had already increased to 7500 Pa.s after 17 days, demonstrating that a quasi solid state was attained. Apparent diffusion coefficients (D(app)) of I(-) and I(3)(-) obtained from the voltammetric measurements were approximately 10(-7) cm(2)/s and decreased to approximately 10(-8) cm(2)/s after 15 days of sol aging. Time-dependent vibrational spectra, which served in assessing the hydrolysis and condensation reactions of MTMSPI(+)I(-), were measured with the help of the attenuated total reflectance (ATR) IR spectroscopic technique. The results revealed that, in the course of condensation of sols, the refractive index of the modes attributed to the polysilsesquioxane species exhibited strong dispersion, which led to a shift of the vibrational band position in the experimental ATR spectra. This effect accompanies the sol-to-gel transformations and has not yet been considered as a possible error in analysis of the ATR spectra of sols and gels. The calculation procedure for obtaining the corresponding transmission spectra is briefly outlined, and the results are applied in this work.