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This work presents the synthesis, structural investigation, and some properties of a new PLA-Siloxane-PEO hybrid featuring covalent bonds between polymers and siloxane nodes. The synthesis simultaneously connecting PLA and PEO chains directly to the inorganic phase is first achieved through the use of sol–gel process. The structural features, thermal properties and chemical stability of this biocompatible system have been studied by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, 29Si Nuclear Magnetic Resonance (NMR), scanning electron microscopy (MEV), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). SEM and SAXS measurements showed that the siloxane nodes act as crosslinks between the polymer chains promoting high miscibility between PLA and PEO. FTIR, Raman XRD, DSC, and TGA showed that the presence of the siloxane nodes diminishes the crystallinity of both polymers and increases their thermal resistance. In addition to the absence of brittleness due to the low crystalline character of PLA, this new material exhibits a fantastic resistance to PLA degradation in aqueous medium, attributed both to the presence of the siloxane particles acting as a barrier towards water diffusion and to the hydrophilic PEO segments which may attract water molecules, preventing PLA hydrolysis. All of these characteristics offer an amazing perspective for the use of this hybrid material in biological, medical, and pharmaceutical applications.

In this work, silica capsules containing bromothymol blue (BTB) were synthesized by a modified Stober sol–gel method. These silica capsules were dispersed into a high-density polyethylene (HDPE)/ethylene-vinyl acetate (EVA) polymeric matrix and then applied in milk spoilage detection tests. The effect of the KOH/BTB molar ratio used in the sol–gel synthesis on the structural, textural, and morphological characteristics of the resulting silica capsules was also investigated. Field emission gun scanning electron microscopy images of the silica capsules showed particles with spherical morphology and size ranging from 0.1 to 1 µm. All silica capsules presented a very low porosity and an encapsulated BTB content in the range of 12–37 µmol g−1. The increase of the KOH/BTB molar ratio resulted in an increase in the relative amount of six-fold siloxane rings and a decrease in the BET surface area of the silica capsules. Spoilage kinetics of milk at room and fridge temperature were much different, as evidenced by pH milk measurements. The milk storage temperature and the KOH content in the silica capsules affected the intensity and rate of blends color change. Blends (HDPE/EVA/silica capsules) with lower KOH content in the capsules showed faster kinetics and higher intensities of color change during the milk spoilage at both tested temperatures. These results showed the potential of the HDPE/EVA/silica capsules as a base material to a sensor packaging, which allows the verification of the milk quality by the end-users.

Molecular structures of siloxane materials should be highly controlled for achieving advanced functionalities. However, it is still difficult to precisely control the structure of siloxane materials by the sol–gel processing. In the present study, we focused on the silanol groups in the intermediate oligomers and resultant siloxane materials as a key structural unit for controlling the molecular structure. Thermal stability and chemical reactivity of silanol groups were found to be highly dependent on the steric effects of the surrounding side chains and siloxane skeletons. The present work suggests that controlling the steric effects around silanol groups in the intermediate oligomers allows modulating the crosslink density of siloxane skeletons. The selective molecular modification tunes the structure and chemical properties of the resultant siloxane materials.

Novel bridged silsesquioxanes (BSs) incorporating short oligo(oxypropylene) or oligo(oxyethylene) chains bonded to a siliceous network via urea cross-links were synthesized by the sol–gel process from the organosilane precursors (CH3CH2O)3-Si-(CH2)3-NHC(=O)NH-R-NH(O=C)NH-(CH2)3-Si-(OCH2CH3)3, with R≡-[CH(CH3)CH2O]xCH2CH(CH3)- (x∼2.5 and 6.1) or R≡-(CH2)2O(CH2)2O(CH2)2-, respectively. The new BSs were identified by the notations d-U′(Y′) with Y′ = 400 and 230, and d-U(Y) with Y = 148, where d stands for di, and U/U′ denote the urea group. The hybrid materials were produced as transparent, amorphous, homogeneous, and soft monoliths, although d-U(148) presented some rigidity. In the three samples the siliceous framework is mainly composed of [–(CH2)Si(OSi)3] and [–(CH2)Si(OSi)2(OH)] substructures. The highest polycondensation degree of the siloxane network was found in the case of d-U′(400), pointing out the formation of a three dimensional framework. In the three materials the urea groups are extensively involved in the formation of strong ordered urea-urea hydrogen-bonded aggregates of different degree of order. The d-U′(230) BS is a promising candidate as mold material for micropatterning applications aiming the fabrication of smart coatings. The prospects for these materials in flexible electrochromic devices for smart windows, where they can act as outermost substrates, are also excellent.

Fossils are nonrenewable natural heritages formed by Mother Nature. After being excavated or exposed, fossils can be destroyed by weathering and water erosion. However, until now, there is very limited research work on fossil conservation. In this work, we focus on the protection of pterosaur fossils found in Hami, which are very sensitive to water. Four siloxane-based polymeric sols, including from tetraethyl orthosilicate and other three hybrid siloxane monomers, are prepared by controlled hydrolysis protocol. Their chemical and physical properties and performances as fossil protection materials are examined. Experimental data show that all sols have excellent permeabilities, decent reinforcement abilities, good resistance to light and heat aging. The organic moieties in the hybrids can also significantly increase the fossil’s hydrophobicity and reduce the cracking of the gels. The results indicate siloxane-based polymers can be very potential protection materials for fossils. And the hybrid polysiloxane sol containing epoxy function groups has overall the best performances.

A series of SiO2-, and CoxOy-modified-TiO2 colloids prepared by hydrolysis of titanium alkoxide were synthesized. The effects of concentrations of water, acid, cobalt chloride, and tetraethoxysilane on the characteristics of colloids were investigated. The rheologic characteristics of the sols were characterized by liquid state 29Si nuclear magnetic resonance (NMR), Raman spectroscopy, and photon correlation spectroscopy. It was found that an increase in the acid concentration from 1 to 60 mM resulted in a decrease of the particle size from 17 to 9 nm, while the diffusion coefficient increased with twofold. The presence of water shortened the formation time of sol, and the specific concentration of hydrochloric acid stabilized the colloid system. The presence of Co(II) chloride enhanced the hydrolysis rate of tetraethoxysilane and the condensation rate of hydroxy derivatives. In contrast, Ti(IV) tetra-n-butoxide showed the opposite effect, slowing these processes and decreasing the degree of condensation of siloxane chains. The results of this study can be used to optimize the composition of stable homogeneous solutions to synthesize TiO2, TiO2–SiO2, TiO2–CoxOy, and TiO2–SiO2–CoxOy sols.

Tetraethoxysilane-derived silica sols stable to sedimentation as well as kinetically and “sol-gel@paint” compositions based on beeswax dissolved in tetraethoxysilane with addition of polyorganosiloxanes, siloxane block copolymer, and hydrophobized aerosil synthesized within this study served as a base for the development of a new technique for preparation of coniferous wood protective coatings. The surface morphology of the coatings was investigated along with their chemical composition, hydrophobicity/hydrophilicity, and adhesion and water absorption. The laboratory tests for biostability with respect to wood-destroying fungi and full-scale climatic tests in the conditions of Extreme North of Russia were performed upon the pine wood coated with developed coatings and their results are presented in this study.

Ultraviolet (UV)-curable and highly condensed (>86%) methacrylate phenyl oligo-siloxane (MPO) was synthesized by non-hydrolytic sol–gel condensation reaction between methacrylate and phenyl silane precursor. The MPO resin was then cured by an UV-initiated free-radical polymerization to fabricate a transparent (>90% at 550 nm) methacrylate–siloxane hybrid material (methacrylate hybrimer). An urethane butanediol dimethacrylate (UBDM) monomer was synthesized as a cross-linker into the methacrylate hybrimer networks without micro-phase separation. The UBDM increased methacrylate conversion and mechanical properties due to the hydrogen bonding of the urethane linkage. The hardness, modulus, and strength were improved by UBDM insertion, the flexibility was even increased with 140% elongation, compared to neat MH. In addition, a storage modulus related to the thermo-mechanical properties was also enhanced by a denser cross-linkage with the urethane linkage.

A novel organized di-urethane crossed-linked dodecyl/siloxane (di-alkyl-urethanesil) was synthesized by the sol–gel process and self-directed assembly, from the organosilane precursor (CH3CH2O)3-Si-(CH2)3-NHC( = O)O-(CH2)12-O(O = C)NH-(CH2)3-Si-(OCH2CH3)3, through a fine control of the reaction conditions (hyper-stoichiometric amount of water, minor amount of tetrahydrofuran, and acid catalysis; molar ratio Si:H2O:HCl:THF = 1:300:0.1:12.5). The new bridged silsesquioxane was identified by the notation d-Ut(CY)AC, where Y = 12 is the number of carbon atoms C of the bridging alkyl chains and AC represents acid catalysis. The d-Ut(C12)AC material exhibits a structured lamellar organization with medium long-range order, a texture composed of homogeneous lamellae immersed in a sponge-like matrix made of randomly distributed thin plates, and is thermally stable up to ca. 350 °C. Despite the hydrophobic nature of the dodecane chains, the weakness of the urethane–urethane hydrogen-bonded array formed led to the growth of moderately ordered assemblies of amphiphilic organo(bis-silanetriol) substructures comprising mainly all-trans conformers.

In sol-gel chemistry, hydrolysis is the key step in the formation of the reactive hydroxide groups that are responsible for the formation of inorganic networks via the occurrence of condensation reactions. Though previous studies have investigated the effect of the hydrolysis conditions on the structure of organically modified silicates (ormosils), no study, to our knowledge, has investigated this variable on the structure of hybrid materials prepared by combinations of an ormosil and a transition metal (TM). Here, we propose to investigate this effect in a hybrid material composed of 3-trimethoxysilylpropylmethacrylate and a zirconium complex. To also highlight the effects of the precursor’s concentrations on the hydrolysis and condensation reactions of the hybrid materials, their relative content was altered along with the hydrolysis degree. The anticorrosion barrier properties were identified by characterisation of coatings deposited on AA2024-T3 substrates and correlation between the structure and the anticorrosion properties of the coatings were performed based on results obtained from structural characterisations (DLS, FTIR, 29Si-NMR, DSC, AFM and SEM) and corrosion testing (EIS and NSS). It is demonstrated that competition in the formation of siloxane and Si-O-Zr bonds takes place and can be controlled by the degree of hydrolysis and the concentration of the zirconium complex. This effect was found to dramatically alter the morphology of the coatings and their subsequent anticorrosion performances. At short-term exposure times, it is found that the most condensed materials exhibited a higher corrosion resistance while over longer periods the performances were found to level. This article highlighted the critical impact of the hydrolysis degree and zirconium concentration on the connectivity of hybrid sol-gel coatings and the impact this has on corrosion performances.

Disiloxanetetraols are very useful synthetic precursors for various siloxane compounds. In addition, they are effective starting materials in sol–gel chemistry for the fabrication of well-defined structures. We herein described a facile single-step synthesis of disiloxanetetraols ([RSi(OH)2]2O) with various substituents (R = Pr, i-Pr, i-Bu, cyclopentyl, hexyl, cyclohexyl, Ph) by hydrolytic condensation of trichlorosilanes, where the reaction was quenched at an early stage. [PrSi(OH)2]2O has the smallest substituents among the disiloxanetetraols reported so far. The results of X-ray crystallography of [C5H9Si(OH)2]2O showed a supramolecular sheet structure formed by intermolecular hydrogen bonding. We also found that disiloxanetetraols and cyclotetrasiloxanetetraols with isobutyl groups can be synthesized from isobutyltrichlorosilane by simply changing the quenching time and reaction temperature.

The continuous wet chemical preparation of micro- and nanoparticles is a major challenge for the large-scale production of functional colloids. Here we present a general synthetic strategy for sol–gel-based materials via an additive free homogenous approach avoiding emulsion-based systems. A variety of different silica and organically-modified silica (ORMOSIL) spherical particles were prepared applying a condensation of prehydrolyzed alcoholic solution of organotrialkoxysilanes in a microjet reactor. This method presents a unique wet chemical production method for nano- and microscale materials. Methyl-, ethyl-, propyl-, vinyl-, phenyl-, and mixed ORMOSIL particles in the range of 75 nm–2 µm were successfully synthesized without the addition of stabilizing surfactants. The method was also investigated for the continuous preparation of pure silica particles, and we succeeded to produce continuously up to 23 g particles per minute. The influence of different organic groups on the crosslinking of the siloxane network was systematically studied applying various spectroscopic and thermoanalytical methods. The degree of condensation of the obtained particles depends on the organic rests of the trialkoxysilanes, which was studied with 29Si CP-MAS NMR. We were able to show that phenyl silsesquioxanes show less condensation in the particles than smaller alkyl or vinyl groups. In addition, the silane concentration has a significant influence on the particle size. Generally, smaller particle diameters are obtained after decreasing the silane concentration. The described process delivers a fast and large scale wet chemical production of various silsesquioxane and silica particles without the use of additives and is therefore suited for a variety of potential applications where high purity of the particles is necessary.

Mesoporous, interlayer-free, hybrid carbon-silica membranes based on organosilica of triethoxyvinylsilane (TEVS) and pluronic triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (P123) were successfully prepared by modified acid-base catalysed sol–gel method. Xerogels and membranes were pyrolyzed under inert conditions in vacuum and nitrogen to form the hybrid carbon silica structures. FTIR analyses showed the presence of Si–C groups in addition to silanol and siloxane groups for samples pyrolysed at 450 °C. Vacuum pyrolyzed xerogels produced slightly higher pore volumes than that of the nitrogen pyrolyzed samples. As a result, the vacuum pyrolyzed membranes produced highest water fluxes compared to the nitrogen pyrolyzed membranes. Best water fluxes were measured at 6.26 (1 wt%, 60 °C) and 2.92 (15 wt%, 60 °C) L m−2 h−1 with salt rejections of 99.7% and 99.9%, respectively. This study demonstrates that the combined strategy of a sol–gel synthesis containing vinyl organosilica and polymeric template followed by vacuum pyrolysis conferred the carbonized silica membranes with excellent selectivity of water from the hydrated salt ions and reasonable water fluxes for water desalination applications.

Vinyl-methyl oligosiloxane resin was synthesized by a hydrolytic sol-gel reaction of vinyltriethoxysilane and dimethyldiethoxysilane. Hydrochloric acid was added as a catalyst to promote the hydrolysis of silane monomers to form a highly condensed siloxane resin (Condensation degree = 95 %). The vinyl-methyl oligosiloxane and hydrogen-methyl oligosiloxane resin was then cured by a thermal hydrosilylation reaction with a minimal platinum catalyst content (3 ppm). The increased cross-linking density improved the thermal decomposition temperature and lowered the weight loss at a high temperature. The fabricated methyl-siloxane hybrid material (hybrimer) shows superior thermal stability (decomposition temperature >530 °C), good long-term thermal resistance (300 °C, 20 h) and transparency (92 % at 450 nm, 83 % at 350 nm) in the visible and ultraviolet ranges. Based on these characteristics, the methyl-siloxane hybrimer can be applied to various applications, including thermally stable optical materials.

Three well-tuned procedures were used for thermal improvement of epoxy resin (E). Accordingly, graphene xerogel (GX) was used as nanofiller in the matrix of E. Additionally, (3-isocyanatopropyl)triethoxysilane-modified E (IE) or tetraethyl orthosilicate (TEOS) oligomer-modified E (TE) was incorporated into a hybrid structure of graphene-containing silica/siloxane network. For this purpose, a bifunctional silane coupling agent of 1,1′-(hexane-1,6-diyl)bis(3-(3-(trimethoxysilyl)propyl)urea) (HDBTMSPU) was synthesized. GX was obtained by incorporation of HDBTMSPU-modified graphene oxide (FGO) into xerogel structure using HDBTMSPU and TEOS. Modified resins, FGO, HDBTMSPU, and TEOS were also used in preparation of hybrid products. Thermal stability and char residue of the composites were compared. GO modification was approved by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman, X-ray diffraction, and thermogravimetric analysis results. Hybrid composite of IE, FGO, and silica/siloxane network shows higher thermal properties. Char residue is increased by 16.93 % by loading of only 1 wt% of FGO in this hybrid product.

Lamellar organosiloxane film has been reported to exhibit a good water vapor barrier property as siloxane compounds because siloxane layer serves as blocking layer for water molecule diffusion. Incorporation of an additional blocking component would further decrease a permeation of water molecules into the film. In the present study, lamellar organosiloxane/graphene oxide (GO) nanocomposite films were prepared by adding GO as a blocking layer. Organosiloxane films of lamellar structure can be obtained even with the GO addition. With the addition of GO into organosiloxane film, the resultant nanocomposite containing 0.037 wt% GO exhibits a minimum water vapor transmittance rate (WVTR) value. The water vapor barrier capability decreases by a further loading of GO because of an increase in a surface roughness of nanocomposite film. The estimated WVTR of a 100-μm-thick lamellar organosiloxane/GO film is reduced to 72 g m−2 d−1 compared to 106 g m−2 d−1 for a lamellar organosiloxane film. This WVTR value of organosiloxane/GO film is about 25 times smaller than that of 100-μm-thick commercial silicone rubber film.

Low-density, transparent aerogels based on a hexylene-bridged polysilsesquioxane ([O1.5Si–(CH2)6–SiO1.5] n ) network have been prepared for the first time via a simple sol–gel process. An optimized base-catalyzed one-step hydrolysis–polycondensation process of a bridged alkoxysilane precursor 1,6-bis(trimethoxysilyl)hexane in a low-polarity solvent N,N-dimethylformamide allows for the formation of a pore structure of a length scale of several tens nanometers, resulting in low-density, transparent aerogels after supercritical drying. Because of the incorporated organic moiety that bridges the silicon atoms in the network, these aerogels show higher flexibility and strength against compression and bending as compared to silica aerogel counterparts. In addition, minimizing the residual silanol groups in the network by a surface modification with hexamethyldisilazane has further improved resilience after compression and bending flexibility and strength, due to the decreased chance of the irreversible formation of the siloxane bonds upon compression. The resulting trimethylsilylated hydrophobic gels have been subjected to ambient pressure drying to obtain xerogels, resulting in low-density (0.13 g cm−3, 90 % porosity), transparent (71 % transmittance) xerogels. These results are promising for the development of transparent thermal superinsulators applicable to window insulating systems that manage heat transfer in a more efficient way.

An azobenzene (AZO)-bridged cubic silsesquioxane network exhibiting reversible photoisomerization behavior in nonpolar solvents has been prepared via hydrosilylation reaction between 4,4′-diallyloxy-azobenzene and octahydridosilsesquioxane (H8Si8O12; H-POSS). Approximately 70 % of the corner Si–H groups of H-POSS are reacted to form a three-dimensional gel network while maintaining the cubic siloxane structure. The dried gel has a high thermal stability, which is attributed to the highly cross-linked cubic silsesquioxane network where AZOs are covalently incorporated in the main chain. The gel exhibits reversible swelling behavior in nonpolar solvents during wetting–drying cycles. In toluene, a large extent of reversible trans–cis isomerization of the AZO moiety is observed. These results are promising for the design of a new class of photoresponsive materials applicable in host–guest chemistry.

Sensors bearing functional units that could transform the chemical recognition into readable signals due to binding to single or even more targets have received much attention. Here, two F−/Cu2+ optical sensors based on lanthanide edifices were designed. The f–f forbidden transitions of lanthanide elements differ significantly from organic compounds since they exhibited favorable features such as narrow emissions and high color purity. Europium(III) complex of 2-(3-carboxyphenyl)imidazo[4,5-f]-1,10-phenanthroline (Eu-1) and europium(III) ternary complex of 2-(3-carboxyphenyl)imidazo[4,5-f]-1,10-phenanthroline and dibenzoylmethane (Eu-2) showed on–off changes in responses to the guest species. The excitation wavelength of Eu-2 could be extended to nearly visible light range, and this longer wavelength sensitisation will be useful in the selection of cheap laser sources. Generally organic complexes suffered from the instabilities in practical uses, the encapsulation of indicators into hosts will be necessary. Therefore, the lanthanide containing hybrid films which were composed of cross-linked siloxane and polymeric matrices were also prepared. The inorganic–organic film could be excited at 410 nm and demonstrated improved thermal stability. Moreover, we could detect F− and Cu2+ in aqueous mixed solution and this feature would be favorable for future uses. F−/Cu2+ optical lanthanide sensors were designed. The excitation wavelength of europium(III) complex with 2-(3-carboxyphenyl)imidazo[4,5-f]-1,10-phenanthroline and dibenzoylmethane (Eu-2) could be extended to nearly visible light range. Moreover, the Eu-2 doped film with cross-linked siloxane and polymeric hosts was also prepared.

The various stages of the TEOS-based sol–gel process were studied by EPR spectroscopy using a VO(II) spin-probe. A detailed analysis of the multicomponent VO(II) EPR spectra recorded at 77 K showed that three main types of individual signals appeared superimposed at the various stages of the sol–gel process, which corresponds to different environments of the paramagnetic VO(II) cations. The spin Hamiltonian parameters of each individual subspectrum remain unchanged throughout the various stages of the sol–gel process. However, the relative contribution of individual signals changed significantly as the sol–gel process proceeded. The results show that the VO(II) cations are not directly incorporated into the siloxane network, but are trapped relatively freely as [VO(H2O)5]2+ complexes in a solution-like environment during the evolution of the sol–gel process. It was amply demonstrated that the sol-to-gel transformation from the viscous, colloid suspension to the viscoelastic gel can be successfully monitored by EPR spectroscopy with VO(II) as a spin-probe.

Polysiloxanes were prepared by acid-catalyzed controlled hydrolytic co-polycondensation of polymethyl(methoxy)siloxanes (PMS) and polymethoxysiloxanes (PMOS) obtained as macromonomers by acid-catalyzed controlled hydrolytic polycondensation of methyl(trimethoxy)silane and tetramethoxysilane, respectively. Co-polycondensation of the macromonomers with molecular weights M w 2000 (PMS) and 400 (PMOS) provided polymethylsiloxane copolymers with molecular weights M w 6500–15,000. The structure was confirmed to consist of block copolymers poly(PMS-block-PMOS) based on the results of gel permeation chromatography, isolation by fractional precipitation with THF and hexane, and 1H and 29Si NMR spectral analyses. The copolymers were soluble in organic solvents, except for hexane, and were fairly stable to self-condensation even without an end block. Transparent and flexible free-standing films were obtained from a 20 wt% THF solution of polymers. The surface morphology of films by FE-SEM and IR microscopic spectral analyses revealed cross-shaped crystalline materials on the film surface of poly(PMS-block-PMOS); these materials consisted of silsesquioxane unit structures depending on the compositions of PMS and PMOS. Polysiloxanes were prepared by acid-catalyzed controlled hydrolytic co-polycondensation of polymethyl(methoxy)siloxanes (PMS) and polymethoxysiloxanes (PMOS). The structure was confirmed to consist of block copolymers poly(PMS-block-PMOS). The surface morphology of transparent and flexible free-standing films revealed cross-shaped crystalline materials on the film surface of poly(PMS-block-PMOS); these materials consisted of silsesquioxane unit structures depending on the compositions of PMS and PMOS.

An organic–inorganic hybrid was prepared by simply mixing a fullerene derivative with polymethoxysiloxane. First, C60 was subjected to a radical addition reaction with 4,4′-azobis(4-cyanovaleric acid) to provide a C60 derivative. Polymethoxysiloxane was prepared by a controlled hydrolytic condensation of tetramethoxysilane. These two compounds were mixed and heated to provide hybrid bulk body. The hybrid bulk body showed high mechanical strength and elastic modulus compared with polymethoxysiloxane or the C60/polymethoxysiloxane hybrid. The formation of a dense siloxane network was established by a homogeneous mixing of the C60 derivative with polymethoxysiloxane.

Soluble bridged polysilsesquioxanes with a range of molecular weight were synthesized from bis(triethoxysilyl)ethane, ethylene, and acetylene (BTES-E1, -E2, and -E3) via hydrolysis and polycondensation reaction by adjusting the water amount. Polymerization behavior of these three trialkoxysilanes was investigated by monitoring the reaction progress by GPC, and 29Si NMR spectrometry of the resulting polymers, poly(BTES-E1), poly(BTES-E2), and poly(BTES-E3), showing that BTES-E1 generated cyclic oligomers at the early stage. In contrast, polymerization of BTES-E2 and BTES-E3 provided no detectable amounts of cyclic oligomers, but afforded linear polymers only. Bulk gels were also prepared by curing the polymers. The gel from poly(BTES-E3) exhibited high thermal stability derived from the rigid acetylene spacer with respect to thermogravimetric analysis. On the other hand, the polymer film of BTES-E1 showed the highest pencil hardness index among the polymers, indicating the tight siloxane network of poly(BTES-E1).

For functional hybrid materials with desirable physical properties as well as chemical characteristics, controlled modification, i.e., site selective modification, of inorganic networks is one of the promising approaches. Here, we report a selective modification of less-condensed Si atoms in a siloxane-based UV-cured resin can drastically improve thermal crack resistance. The highly improved thermal crack resistance is attained by elimination of monomeric Si alkoxides using trimethylchlorosilane (TMCS) as a modifier. Liquid- and solid-state 29Si NMR analyses were performed to evaluate the selectivity of reaction between TMCS and monomeric Si alkoxides included in photocurable precursory sols, whereas thermal mechanical analysis was to estimate coefficients of thermal expansion and deformation temperature of the UV-cured resins. The reaction between TMCS and the UV curable precursory sol occurs via a moisture-assisted process involving moderate hydrolysis reactions. As a result, the addition of TMCS increases a temperature at which crack forms from 150 up to 300 °C.

Paper is an organic material widely used in cultural heritage and mainly composed of cellulose mixed with lignin, hemicellulose and small amounts of additives. This paper deals with siloxane coatings on pure cellulose paper, applied by sol–gel dipping in sols prepared with different siloxane precursors (tetraethoxysilane, methyl triethoxysilane, dimethyl diethoxysilane, trimethyl monoethoxysilane). The coated samples were characterized using various techniques (Fourier Transform Infrared Spectroscopy FT-IR, Nuclear Magnetic Resonance NMR and Scanning Electron Microscopy and Energy Dispersive Spectroscopy SEM–EDS), measuring their mechanical properties, flame resistance and contact angles, and a colorimetric test. The coated samples’ behavior was more hydrophobic the higher the methyl number of siloxane precursor, regardless of the coating’s thickness. Increasing the thickness improved the mechanical and thermal properties. The thickest coatings were obtained using a double coating process and a basic catalyst for the hydrolysis step, but this latter condition facilitated the formation of surface agglomerates, which make the paper too stiff and yellow.

International audience; Hydridosilazane compounds containing Si-N and Si-H bonds can be used as precursors of SiOx materials. The hydrolysis-condensation reactions of tetramethyldisilazane, as a polyhydridosilazane model compound, were investigated by H-1 and Si-29 liquid NMR spectroscopy. These reactions were carried out at room temperature for up to 120 min in presence of water. The identified products are short linear siloxane species (hydride terminated polydimethylsiloxanes (MDxMH)-D-H) and cyclosiloxanes. Silicon hydride persistence in the reactional mixture suggested that silazane group is more sensitive to hydrolysis reaction than silicon hydride group. Moreover, additional experiments evidenced that the low steric hindrance of the silicon hydride influences the silazane hydrolysis kinetic. Hence the presence of ammonia released during silazane hydrolysis reaction was demonstrated to be a catalyst of the silicon hydride hydrolysis reaction.

This paper presents a study regarding the formation of hybrid gels starting from tetraethyl orthosilicate (TEOS), polyvinyl alcohol (PVA) and 1,3-propanediol (PD) and their thermal evolution to mesoporous silica matrices. The possibility of obtaining homogenously dispersed cobalt ferrite inside the silica matrix starting from (TEOS–PVA–PD–Metal Nitrates) gels was also studied. The formation of the hybrid gels TEOS/PVA/PD with different compositions was studied by FT-IR spectrometry and thermal analysis, in order to evidence the interaction between the diol with the organic and the inorganic polymers. Both thermal analysis and FT-IR spectrometry have evidenced the formation of physical and chemical interaction between polyols and the siloxane network. Elemental mapping performed by SEM-EDX technique evidenced the formation of homogenous hybrids both in the presence of the absence of 1,3-propanediol. SEM images of the powders obtained by annealing the hybrid xerogels at 600 °C have evidenced the formation of mesoporous silica. By thermal treatment of the (TEOS–PVA–PD–Metal Nitrates) gels, 30%CoFe2O4/70%SiO2 (mass percent) nanocomposites uniformly dispersed in silica matrix with characteristic magnetic properties, have been successfully synthesized.

Novel yellow and blue emissive dyes have been synthesized using 2,5-diamino-3,6-dicyanopyrazine and various alkoxysilanes and they are covalently bridged to cycloaliphatic epoxy functional oligosiloxane via non-hydrolytic sol–gel reaction. Dye-bridged hybrid materials (DBH) are fabricated by thermal curing the dye-bridged oligosiloxane. Structure and formation of dyes and siloxane network is studied using analysis method. Four components of red, yellow, green and blue emitting DBH cover entire visible range and white luminescence with high color rendering index is realized by controlling their combinations. We have ensured superior thermal stability DBH at 120 °C for 200 h caused by covalently bridged structure and robust siloxane matrix.

Cotton fabric was treated with two-component water- and oil-repellent antimicrobial coatings consisting of the commercial aqueous organic–inorganic hybrid precursors fluoroalkyl-functional siloxane (FAS) and 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride (SiQAC) of different concentrations. Two different application procedures were used: a one-step treatment (S1) by a sol mixture consisting of both precursors [coating FAS-SiQAC (S1)] and a two-step treatment (S2) by SiQAC sol and then FAS sol [coating SiQAC + FAS (S2)]. The functional properties of the coatings were determined from liquid contact angle measurements and antimicrobial activity, as well as FTIR and XPS analyses. Although both treatments gave the cotton fabric superhydrophobic and oleophobic properties at a sufficient sol concentration, procedure S1 was found to be more effective than procedure S2. The antibacterial properties of the SiQAC + FAS (S2) coating were superior to those of the FAS-SiQAC (S1) coating. For both two-component coatings, the active bacteriostatic activity of SiQAC was enhanced by the passive antibacterial activity of FAS. Two-component coatings did not provide significant antifungal protection. Repetitive washing gradually deteriorated both coatings but the coating applied by procedure S2 seemed to be slightly more durable than that applied by S1. The two-component coatings caused an increase in the flexibility and a slight decrease in the fabric breaking strength and air permeability of the cotton sample.

A high thermal-stable methacrylate-silicate hybrid nanocomposite (hybrimer) was fabricated based on UV-induced polymerization of a highly-condensed methacryl-oligosiloxane resin (Hy-MO). The Hy-MO resin was newly synthesized via an acid-catalyzed hydrolytic sol–gel reaction of 3-(methacryloxy) propyl trimethoxysilane (MPTS) and diphenyldimethoxysilane. The basic properties of Hy-MO were compared with a conventional resin prepared by a Ba(OH)2·H2O-catalyzed non-hydrolytic sol–gel reaction of MPTS and diphenylsilanediol (N-MO). It was found that Hy-MO have a higher siloxane condensation degree, larger molecular size and weight than the N-MO due to the highly mobile proton ions that effectively catalyze the overall sol–gel reaction. The resultant Hy-MO hybrimer showed a higher thermal stability than N-MO hybrimer.

A series of aminopropyl-silica-magnesia hybrid materials has been prepared by the sol–gel method from tetraethoxysilane (TEOS), magnesium chloride (MgCl2) and aminopropyltriethoxysilane (APTES) under acid conditions. The APTES:TEOS ratio was varied between 0:1 and 1:0. The aminopropyl coverage concentrations for APTES-silica-Mg samples were in the range of 0.3–2.3 mmol g−1. The hybrid materials were characterized by numerous techniques, including X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Fourier transform Raman spectroscopy (FT-Raman), solid-state 13C and 29Si nuclear magnetic resonance (13C- and 29Si-NMR), thermogravimetry (TGA), N2 adsorption–desorption, small-angle X-ray scattering (SAXS), and scanning electron microscopy (SEM). The increase of APTES content in the silica network resulted in the increase of six-membered siloxane rings. The hybrid systems were shown to be formed from fully-condensed, trifunctional APTES species. The porosity and morphology of the hybrid materials were influenced by the initial TEOS/APTES ratio. The radius of gyration of the primary particles, determined by SAXS, was between 1.1 and 2.9 nm.

Methacrylate zirconium siloxane (MZS) resin was synthesized by a sol–gel reaction of 3-(trimethoxysilyl)propyl methacrylate, diphenylsilanediol, and zirconium n-propoxide chelated with methacrylic acid. Also, propylene glycol monomethyl ether acetate was added as a solvent to synthesize a homogeneous and long-term stable resin by controlling the reactivity among the precursors. A High condensation degree of the resin and the formation of Si–O–Zr hetero-metal bonds were verified by 29Si NMR and FT-IR spectroscopy. The MZS resin was spin-coated and photo-polymerized to fabricate a highly transparent MZS hybrimer coating film. The refractive index and dielectric constant of the film increased according to the zirconium content, up to 1.59 and 3.65, respectively.

Free silanol groups of silica-gel functionalized with quercetin (QSG) were blocked with TiO2 or ZrO2 to produce TiO2-QSG and ZrO2-QSG, respectively. The silica materials were characterized by infrared, Raman spectra, thermogravimetric, elemental analyses, magic angle spinning 13C-nuclear magnetic resonance, BET specific surface area measurements and inductively coupled plasma—optical emission spectrometry-monitored silica hydrolysis. Siloxane groups are reinforced in the blocked QSG samples without affecting the hydrophilic nature or the porosity of silica. Quercetin is unaffected by the titania layer in contrary to zirconia. Also, the stability of silica against hydrolysis in TiO2-QSG and ZrO2-QSG was remarkably improved in the range of pH 3.5–9.1, attributed to the interruption of the intramolecular interaction of silanol groups with the amino groups. The hydrolyzed silica of TiO2-QSG and ZrO2-QSG decreased to 46.6 and 18.5%, of that of QSG and to 7.6 and 3.1%, of that of 3-aminopropylsilica gel at pH 9.1, respectively. TiO2-QSG was applied for the extraction of Hg(II) with separation efficiency of 99.0 ± 0.6% at pH 8.5. The capacity loss of TiO2-QSG per recovery cycle of Hg(II) was lowered in comparison with the uncovered material. It was successfully applied for the recovery of Hg(II) from spiked water and referenced samples.

A mesostructured silica-based material was synthesized by self-assembly of a novel amphiphilic molecule consisting of a well-defined siloxane head with a double five-ring (D5R) structure and a hydrophobic alkyl tail. A precursor functionalized with ethoxy groups, C22H45Si10O15(OEt)9 (1), was hydrolyzed under an acidic condition with the retention of the D5R units, leading to the formation of two-dimensional (2D) hexagonal phase by evaporation-induced self-assembly of amphiphilic hydrolyzed molecules. Solid-state 29Si MAS NMR analysis of the resulting hybrid solid confirmed that the D5R units were cross-linked to form siloxane networks. Calcination of this hybrid solid gave mesoporous silica with high BET surface area (740 m2 g−1). These results expand the design possibility of silica-based materials at both molecular- and meso-scales, leading to the bottom up synthesis of hierarchically ordered materials.

Hybrid melting gels were prepared by a sol–gel process, starting with a mono-substituted siloxane and a di-substituted siloxane. Methyl-modified melting gels were prepared using (a) methyltriethoxysilane (MTES) with dimethyldiethoxysilane (DMDES) and (b) methyltrimethoxysilane (MTMS) together with dimethyldimethoxysilane (DMDMS). The gels with MTES–DMDES were prepared with concentrations between 50–50 and 75–25 mol%. The gels with MTMS–DMDMS were prepared with concentrations between 50–50 and 70–30 mol%. For both systems, the consolidation temperature, after which the melting gel no longer softens, increased with an increase in the amount of the mono-substituted siloxane, increasing from 135 to 160 °C for MTES–DMDES and increasing from 145 to 170 °C for MTMS–DMDMS. Coatings formed on mica substrates were about 1 mm thick, and showed no visible cracks. The surfaces of the coatings were profiled using micro-Raman spectroscopy, which revealed that methyl groups were concentrated at the surfaces of the films. All contact angles measured with water were greater than 90°.

In this study surface-functionalized zirconium oxoclusters (ZrNBB), formed by reaction between vinylacetic acid and zirconium propoxide, were chemically modified through condensation with siloxane groups, so that the core integrity of ZrNBB was preserved. The direct coupling between zirconium oxo-clusters and siloxane moiety was performed by co-polymerisation with vinyl trimethoxysilane (VTMS) with Zr:Si molar ratio 1:2 in air at room temperature and benzoyl peroxide (BPO) was used as an initiator to start radical polymerization. The polymerisation was studied by differential scanning calorimetry (DSC) and Fourier Transform Infra Red (FTIR) spectroscopy. 29Si and 13C liquid and solid state NMR analyses were performed in order to study the microstructure of the hybrid material and the role of the clusters in polymerization and condensation. Beyond this, shear storage modulus (G′) and loss modulus (G′′), were investigated by dynamical mechanical spectroscopy (DMS). The results indicated a great stability at high temperature without any viscous flow during glass transition.

Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres were prepared from a commercially available fluoroalkylfunctional water-born siloxane (FAS) (Degussa), nanosized silver (Ag) (CHT) and a reactive organic–inorganic binder (RB) (CHT). Two different application procedures were used: firstly, one stage treatment of cotton fabric samples by FAS sol (i), as well as by a sol mixture constituted from all three precursors (Ag–RB–FAS, procedure 1S) (ii), and secondly, two stage treatment of cotton by Ag–RB sol and than by FAS sol (Ag–RB + FAS, procedure 2S) (iii). The hydrophobic and oleophobic properties of cotton fabrics treated by procedures (i)–(iii) before and after consecutive (up to 10) washings were established from contact angle measurements (water, diiodomethane and n-hexadecane) and correlated with infrared and XPS spectroscopic measurements. The results revealed that even after 10 washing cycles cotton treated with Ag–RB + FAS (2S) retained an oleophobicity similar to that of the FAS treated cotton, while the Ag–RB–FAS (1S) cotton fibres exhibited a loss of oleophobicity already after the second washing, even though fluorine and C–F vibrational bands were detected in the corresponding XPS and IR spectra. The antibacterial activity of cotton treated by procedures (i)–(iii) was tested by its reduction of the bacteria Escherichia coli and Staphylococcus aureus following the AATCC 100-1999 standard method and EN ISO 20743:2007 transfer method. The reduction in growth of both bacteria was nearly complete for the unwashed Ag–RB and Ag–RB–FAS (S1), but for the unwashed Ag–RB + FAS (S2) treated cotton no reduction of S. aureus and 43.5 ± 6.9% reduction of E. coli was noted. After the first washing, the latter two finishes exhibited nearly a complete reduction of E. coli but for the Ag–RB treated cotton the reduction dropped to 88.9 ± 3.4. None of the finishes retained antibacterial properties after 10 repetitive washings. The beneficial and long-lasting low surface energy effect of FAS finishes in the absence of Ag nanoparticles, which led to the “passive” antibacterial properties of FAS treated cotton fabrics, was established by applying the EN ISO 20743:2007 transfer method. The results revealed a reduction in bacteria of about 21.9 ± 5.7% (FAS), 13.1 ± 4.8% (Ag–RB–FAS (S1)) and 41.5 ± 3.7% (Ag–Rb + FAS (S2)), while no reduction of the growth of bacteria was observed for cotton treated with Ag nanoparticles after 10 repetitive washings. The physical properties (bending rigidity, breaking strength, air permeability) of finished cotton samples were determined, and showed increased fabric softness and flexibility as compared to the Ag–RB treated cotton, but a slight decrease of breaking strength in the warp and weft directions, while air permeability decreased for all type of finishes.

Nonporous films were formed on polypropylene (PP) films using 3-aminopropyltriethoxysilane (APTEOS) as the only precursor. The PP film was modified by corona-plasma treatment to provide appropriate adhesion between coating layer and substrate. Gas permeation properties of coating films were evaluated, and the influences of water ratio and film storing time on the gas permeability were investigated. Structural and surface properties of coating layers were characterized by 29Si-NMR, FT-IR, and contact angle analyzer. The APTEOS coating films exhibit much higher barrier properties than PP film. The permeability coefficient of APTEOS coating film with water ratio of 3 is 0.011Barrer for nitrogen, 0.044Barrer for oxygen, and 0.002Barrer for carbon dioxide, while each permeability coefficient of PP bare film is 0.233, 0.858, and 2.886Barrer, respectively. The gas permeability coefficient is increased slowly along with storage time. Although additionally formed siloxane network may lead to a higher inorganic network density, the enhancement of gas permeability during storing period is largely attributed to film-swelling effect by the water vapor from atmosphere.

To extend the concept of the Cerasome, an organic-inorganic vesicular nanohybrid, this paper investigates the preparation and characterization of a “mixed” Cerasome. The system consists of a Cerasome-forming lipid 1, a cationic synthetic lipid 2, and a zwitterionic phospholipid 3. Lipid mixtures of 1 and 2 or 1 and 3 were used to prepare the mixed Cerasomes. Their lipid distributions were examined using differential scanning calorimetry (DSC), which showed that 1 and 2 (or 1 and 3) were phase-separated in the mixed Cerasomes. These results seem to be mainly attributable to the polymerizable nature of 1. Results of scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX) showed that 1 and 3 were both incorporated into a single Cerasome, not macroscopically separated to form separate vesicles from each lipid component. Mixed Cerasomes of 1 and 2 showed high morphological stability against a membrane-solubilizing surfactant, incorporating up to 70% of 2. On the other hand, the mixed Cerasomes from 1 and 3 were less stable than the mixed Cerasomes from 1 and 2. This relative instability might be attributable to differences between the mixed Cerasomes from 1 and 2 and 1 and 3 in terms of their vesicular sizes, lipid domain sizes, and their relative effectiveness for siloxane network formation. These results strongly support the formation of mixed Cerasomes that have lipid domains in-plane. Systems described in this study are useful to prepare variously mixed Cerasomes that have different surface functionalities and in-plane lipid distribution, but which have high morphological stability.

A medium molar mass poly(hydrogenomethyl- siloxane), Me3Si(O-SiHMe)nOSiMe3, (PHMS), has been used for preparing poly(hydroxymethylsiloxane) supports (PHOMS) for lipase immobilization. The procedure involved the conversion of PHMS to the corresponding poly(alkoxymethylsiloxanes). Me3Si(OSi(OR) Me/nOSiMe3 (PHMS), their alkaline hydrolysis to form poly(siloxanolates) which were then converted to PHOMS by neutralization. The effect of different catalysts and alcohols (methanol, ethanol, 2-propanol) on the course of poly(alkoxymethylsiloxanes) formation is reported. PHOMS supports were characterized by BET and Hg porosimetry, and the degree of their crosslinking was determined by solid-phase NMR. Fluorescence spectroscopy was used to assess surface polarity and determine lipase loading. The efficiency of lipase adsorbed on these supports was tested in the esterification of stearic acid with propanol in hexane. It was found that the activity of the adsorbates is controlled by their porosity. The addition of an inert addend (e.g. hydrotalcite) in the step of alkaline hydrolysis of poly(alkoxymethylsiloxanes) increases the adsorption efficiency of the supports as compared to PHOMS. The potential application of the biocatalysts, lipase-PHOMS adsorbates, was extended by their encapsulation into a RTV silicone rubber containing Si-substituted poly(imide) as a swelling modifier.

This paper reports a direct jet-based polymerisation by polycondensation approach to forming a self-supporting scaffold structure. The processing technique is electrospraying, which is also known as electrohydrodynamic atomization. A specially formulated ethanolic siloxane sol derived from alkoxysilanes was synthesised and electrosprayed using a ring-shaped ground electrode configuration. The medium was seen to electrospray in the stable cone-jet mode, which later gave rise to the growing or forming of “fir-tree” like structures. The materials were characterised using microscopy, solid state NMR, FTIR, XRD and DSC. Hence this paper explains the direct controlled polycondensation from the siloxane sol and further presents the basis by which these scaffolds take shape.

Hybrid siloxane-polymethylmethacrylate (PMMA) nanocomposites with covalent bonds between the inorganic (siloxane) and organic (polymer) phases were prepared by the sol gel process through hydrolysis and polycondensation of 3-(trimethoxysilyl)propylmethacrylate (TMSM) and polymerization of methylmethacrylate (MMA) using benzoyl peroxide (BPO) as initiator. The effect of MMA, BPO and water contents on the viscoelastic behaviour of these materials was analysed during gelation by dynamic rheological measurements. The changes in storage (G′) and loss moduli (G′′), complex viscosity (η*) and phase angle (δ) were measured as a function of the reaction time showing the viscous character of the sol in the initial step of gelation and its progressive transformation to an elastic gel. This study was complemented by 29Si and 13C solid-state nuclear magnetic resonance (NMR/MAS) measurements of dried gel. The analysis of the experimental results shows that linear chains are formed in the initial step of the gelation followed by a growth of branched structures and formation of a three-dimensional network. Near the gel point this hybrid material demonstrates the typical scaling behaviour expected from percolation theory.

The effect of doping by europium triflate on the nanoscopic structure of organic-inorganic hybrid formed by a siliceous network containing pendant amine-terminated propyl chains, called aminosils, was investigated by Small-Angle X-ray Scattering (SAXS). It appears that the composites exhibit a two-level structure. The first level consists of well-condensed cubic-like siloxane octamers, with a radius of gyration around 2 A. The second level is formed by the aggregation of these siloxane nanodomains to form larger structures, in which the nanodomains are spatially correlated and separated by the organic pendant chains. Europium doping inhibits the aggregation between siloxane octamers, leading to a less compact second-level structure. This can be explained by the Eu3+ coordination close to the external surface of the siloxane nanodomains, as detected by luminescence spectroscopy.

The thermal decomposition behavior of methylsiloxane-based inorganic/organic hybrids containing an inorganic component derived from metal alkoxides such as Si(OCH3)4, Al(OsC4H9)3, Ti(OiC3H7)4 and Nb(OC2H5)5 was investigated by means of thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The decomposition temperature of methyl groups in methylsiloxane-based inorganic/organic hybrids containing an inorganic component derived from metal alkoxides was higher than that in the methylsiloxane-based inorganic/organic hybrid prepared from only CH3Si(OC2H5)3. In particular, when incorporating Nb and Ti inorganic components, methyl groups in methylsiloxane-based inorganic/organic hybrids decomposed at about 100 and 200∘C higher temperatures, respectively, than those in the methylsiloxane-based inorganic/organic hybrid prepared from only CH3Si(OC2H5)3. The incorporation of an inorganic component other than siloxane into methylsiloxane-based inorganic/organic hybrids was found to thermally stabilize the methyl groups of methylsiloxane networks.

Polyvinylpolysilsesquioxane (PVPS) organic–inorganic hybrid gel films comprising polyethylene and siloxane backbone linkages were prepared through two routes: trimethoxy(vinyl)silane (VTS) was first subjected to radical polymerization of the vinyl groups, followed by acid-catalyzed hydrolytic polycondensation of the trimethoxysilyl groups (route A) to afford PVPS; in the second route PVPS was prepared in reverse order (route B). PVPS gel films were transparent and homogeneous. We find that the mechanical and heat-resisting properties correlate both to the degree of polymerization and the degree of cross-linking. Copyright © 2003 John Wiley & Sons, Ltd.

The preparation and NO-adsorption/desorption behavior of Li, Ca and Ba silicates were investigated aiming at the application to a NO x -absorbent. Li silicate was prepared by reaction of HSi(OC 2 H 5 ) 3 with aqueous lithium silicate solution (LSS). Ca and Ba silicates were prepared from gels obtained using CH 3 Si(OC 2 H 5 ) 3 , Si(OC 2 H 5 ) 4 , HSi(OC 2 H 5 ) 3 and alkaline-earth alkoxides. The surface of these silicates indicated the solid basicity of Ho = 9 and adsorbed the acidic gas of NO. FT-IR spectra of the silicates adsorbing NO showed the absorption peaks in the range of 1300-1600 cm -1 corresponding to ionic and covalent nitrate NO - 3 . The complete desorption of adsorbed NO species occurred above 500°C in the Li silicate, above 500°C in the Ca and Ba silicates prepared using CH 3 Si(OC 2 H 5 ) 3 , and above 700°C in the Ba and Ca silicates prepared using Si(OC 2 H 5 ) 4 . Regarding the Ca and Ba silicates, the difference in siloxane structure is thought to cause the difference in adsorption state and desorption behavior of NO.

Sol-gel synthesis of organic-inorganic hybrid materials for planar waveguides and devices has received growing interest due to its low-cost processing and good suitability for doping. Titania is an important optical dopant, but homogeneous incorporation of titania in silica is difficult to be achieved by the conventional sol-gel process (aqueous system) because of the significant difference between the hydrolysis rates of the precursors. In this paper, we report an anhydrous sol-gel process for synthesising titania-doped siloxane polymers. The process consists of a hydrolysis of 3-methacryloxypropyltrimethoxysilane (MPS) with boric acid under anhydrous conditions, and a condensation with dimethyldimethoxysilane (DMDMS), diphenyldimethoxysilane (DPhDMS) and titanium ethoxide (TET). Optical characterisations for the produced titania-doped polymer were performed, and results showed that TET doping is useful for reducing the OH concentration of the synthesised polymer and is also effective for improving the optical quality of spin coatings. DMDMS and DPhDMS are favourable in reducing the birefringence and in increasing the thermostability of the material, and the methacryl groups of MPS are UV-polymerizable, which is useful for low cost fabrication of waveguides by photolithographic process. The results of ellipsometry scanning measurements show that titania is homogeneously incorporated in the hybrid matrix, suggesting that the anhydrous sol-gel process is useful for preparation of UV-sensitive titania-doped siloxane polymers for optical applications.

Gelation mechanisms of lithium-doped Siloxane-Poly(oxyethylene) (PEO) hybrids containing polymer of two different molecular weight (500 and 1900 g/mol) were investigated through the evolution of the electrical properties during the solgel transition. The results of electrical measurements, performed by in-situ complex impedance spectroscopy, were correlated with the coordination and the dynamical properties of the lithium ions during the process as shown by 7Li NMR measurements. For both hybrids sols, a decrease of the conductivity is observed at the initial gelation stage, due to the existence of an inverted percolation process consisting of the progressive separation of solvent molecules containing conducting species in isolated islands during the solid network formation. An increase of conductivity occurs at more advanced stages of gelation and aging, attributed to the increasing connectivity between PEO chains promoted by the formation of crosslinks of siloxane particles at their extremities, favoring hopping motions of lithium ions along the chains.

The preparation of nanostructured organic-inorganic materials by assembling of nanobuilding blocks allows controlling the extent of phase interaction, which in its turn governs structure-properties relationships. We present here the synthesis of siloxane-based nanobuilding blocks prepared by reacting diphenylsilanediol with vinyltriethoxysilane and triethoxysilane. The reaction products were obtained by non-hydrolytic condensation between silanediol and ethoxide groups in inert atmosphere, in the presence of pyridine, triethylamine or butyl lithium. Different synthetic conditions were examined by means of ATR-FTIR and NMR spectroscopies, showing the formation of siloxane bonds. In the case of triethoxysilane the reaction carried out in the presence of pyridine leads to Si–H bond preservation in the final product. Air stable products with improved Si–O–Si hydrolytic stability can be obtained by removal of the base after the reaction completion. The condensation products can be described as a mixture of siloxane rings involving difunctional and trifunctional silicon units.