In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltriethoxysilane [bis(aminopropyl)-terminated polydimethylsiloxane (1000)] (PDMSU) sol-gel hybrid, which forms washing-resistant water-repellent finishes on cotton fabrics, were further investigated. The addition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) to PDMSU resulted in a highly apolar low-energy surface on aluminum with gammaStotal equal to 14.5 mJ/m2 and a DetlaGiwi value of -82 mJ/m2. Mixed PFOTES-PDMSU finishes applied on cotton fabrics increased the water contact angles (thetaw) from approximately 130 degrees (PDMSU) to 147 degrees, also imparting oleophobicity (thetadiiodomethane=130 degrees, thetan-hexadecane=120 degrees) to the finished cotton fabrics. Washing caused breakage of the coating's integrity as established from SEM, which was attributed to the partial removal of PFOTES from the composite films, also shown by subtractive IR attenuated total reflectance (ATR) and XPS spectral measurements made on washed and unwashed fabrics. The antibacterial properties of the PFOTES-PDMSU-finished fabrics were assessed with the transfer method (EN ISO 20743:2007), revealing that the reduction of Escherichia coli bacteria on unwashed cotton fabrics was nearly 100%. Moreover, for washed (10 times) cotton fabrics a much higher bacterial reduction was noted for the PFOTES-PDMSU finishes (60.6+/-10.8%), surpassing PDMSU (30.4+/-6.1%) and commercial fluoroalkoxysilane (FAS) (21.9+/-5.7%) finishes. The structure of PFOTES-PDMSU gels, xerogels, and the corresponding coatings was investigated by analyzing the 29Si NMR and IR ATR spectra and comparing them with the spectra of PFOTES and octameric (T8) PFOTES based polyhedra. The results revealed the tendency of PFOTES to condense in octameric silsesquioxane polyhedra (T8), coexisting in the PDMSU sol-gel network with cyclic tetramers (T4(OH)4) and open cube-like species (T7(OH)3). The presence of -OH-functionalized PFOTES silsesquioxanes, established even in coatings heat-treated at 140 degrees C (15 min), also explained the excellent washing fastness of PFOTES finishes on cotton fabrics. The regenerative nature of the water- and oil-repellent properties of washed PFOTES-PDMSU-finished cotton fabrics was attributed to the surface mobility of the T8 PFOTES based polyhedra, ousted from the coating interior during consecutive washings.

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A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (PDMSU) sol-gel hybrid was synthesized and applied on cotton to make it water repellent. Surface-energy values of PDMSU deposited on an aluminum substrate were determined, and the contact angle for water was assessed for impregnated cotton fabrics. The stability of the coatings was determined by repetitive washing, and their degradation was investigated with the help of the infrared attenuated total reflection (ATR) technique. The structure of PDMSU was studied by ATR and 29Si NMR spectroscopy. The results showed the active role of the urea groups in PDMSU/cotton interface bonding, but washing led to the relaxation of the urea-urea associations, as inferred from the appearance of a new amide II band at 1541 cm(-1).

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.

A quasi‐solid‐state, dye‐sensitized photoelectrochemical solar cell employing a gel electrolyte obtained by sol–gel chemistry is described. The gel electrolyte is based on a ureasil precursor (i.e., a poly(propylene oxide) oligomer end‐capped by triethoxysilane groups through urea bridges) and sulfolane and it incorporates the I3–/I– redox couple. It is shown that the combination of these two reagents prevents crystallization of KI, thus ensuring a long life for the cell and a satisfactory overall efficiency that surpasses 5 %. Cell efficiency increases with temperature. Optimization of gel‐electrolyte performance has been obtained by studying mobility with fluorescence‐quenching techniques complemented by direct‐current conductivity measurements.