Sol-gel derived organic-inorganic hybrid from trialkoxysilane-capped acrylic resin and titania: effects of preparation conditions on the structure and properties

Homogeneous organic-inorganic hybrid materials with high performance were successfully prepared by mixing (3-methacryloxypropyl)trimethoxysilane (MPMS) capped acrylic resin with titania synthesized by sol-gel approaches. The effects of the titania content, the amount of water and nature of catalysts in the sol-gel as well as the ratios of mixed solvents of butyl acetate and ethanol on the structures and properties of the hybrid materials were studied. Higher titania content, larger amount of water and base catalysis in the sol-gel process, as well as the solvent with higher ratio of butyl acetate to ethanol for the hybrids caused larger size and less open structure of titania phase. The hardness, elastic modulus, thermal stability and refractive index for the hybrid materials improved dramatically with increasing titania content. In general, better prosperities, especially mechanical properties, were achieved for the hybrid prepared under lower water content, pH values (such as acid catalysis) and m_B/m_E ratio.     

Preparation of titanium dioxide/polyacrylate nanocomposites by sol–gel process in reverse micelles and in situ photopolymerization

UV‐curable, transparent acrylic resin/titania organic–inorganic hybrid films were prepared by controlled hydrolysis of titanium tetrabutoxide in Span‐85/Tween 80 reverse micelles and the subsequent in situ photopolymerization of the acrylic monomers. UV–vis spectra and atomic force microscopy (AFM) indicated the presence of a nanoscale hybrid composition. The onset of absorption (λ_onset) of titania in the hybrids appeared between 363.4 and 383.5 nm, which exhibited blue shifts relative to that of bulk anatase (λ_onset = 385 nm). The titania content increased rapidly at higher temperature and higher TTB content, whereas it increased slowly with longer post‐thermal treatment times. The refractive index and UV shielding properties of the organic polymer were obviously improved with increasing titania content. AFM images showed the inorganic domains (mean size 25.3–28.8 nm) were uniformly dispersed in the polymeric networks. The roughness parameters of the hybrid material were: toughness, 1.5–2.3 nm; root mean square roughness, 4.5–4.6 nm; and peak and valley distance, 9.7–19.4 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5105–5112, 2006     

Effects of additives on the morphologies of thin titania films from self-assembly of a block copolymer

The effects of additives of poly(methyl methacrylate) (PMMA) and HAuCl₄ on the morphologies of hybrid titania films formed via co-assembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers, titania sol-gel precursor in a selective solvent were investigated. The results show that addition of PMMA or HAuCl₄ has an important influence on the morphologies of hybrid titania films. Addition of PMMA or HAuCl₄ can induce the morphology transition of the PS-b-PEO/titania sol-gel mixture from spherical micelles to vesicles. Therefore, the morphologies of the hybrid films formed on silicon substrate surfaces by spin-coating can be controlled by the addition of homopolymer (PMMA) or inorganic precursor (HAuCl₄) into the PS-b-PEO/titania sol-gel mixtures, allowing access to nanoparticles or nanoporous films. After removing the polymer matrix, nanoparticle aggregates or nanobowl-like structures are left behind on the substrate surfaces.     

Fabrication of polyimide/titania nanocomposites containing benzimidazole side groups via sol–gel process

In recent years, polyimide (PI) hybrid materials have received considerable attention owing to the dramatic enhancements over their pristine state in thermal stabilities, mechanical properties and other special features by introducing only a small fraction of inorganic additives. In this investigation, hybrid nanocomposite films of titanium dioxide (TiO₂) in PI were successfully fabricated by an in situ sol–gel process starting from tetraethyl orthotitanate in the solution of poly(amic acid) in N,N-dimethylacetamide. Neat PI was prepared from the polymerization of 2-(3,5-diaminophenyl)-benzimidazole and pyromellitic dianhydride. The hybrid films were obtained by the hydrolysis–polycondensation of moisture-sensitive titania precursor in poly(amic acid) solution, followed by the elimination of solvents and imidization process. The chelating agent, acetylacetone, was used to reduce the gelation rate of titanium alkoxide. The complete imidization temperature of the poly(amic acid) was delayed; furthermore, the thermal stability of PI was enhanced through the incorporation of the inorganic moieties in the hybrid materials. The chemical and morphological structures of the hybrid materials were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The results show that the TiO₂ particles are well dispersed in the PI matrix with particle size between 15 and 30 nm in diameter.     

The effect of titania content on the physical properties of polyimide/titania nanohybrid films

In this study, a series of PI/TiO₂ nanohybrid materials were prepared from polyamic acid of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride/3,3′-diaminodiphenyl sulfone, and titania precursor by the sol-gel method. The titania content in the hybrid system was varied from 0 to 5 wt %. The physical and mechanical properties of the hybrids such as refractive index, optical transmission, and tensile strength were investigated. It was determined that incorporation of titania precursor into the PI matrix improved the refractive indices and tensile modulus of the hybrid films. It was observed that the optical transmittance and tensile strength of the nanohybrids were slightly decreased with the increasing titania content. It was determined that the hybrid films might have enhanced the UV shielding properties compare to the PI films. Furhermore, the hybrid materials showed better thermal stability than the PI. SEM studies demonstrated that titania particles (1 and 3 wt %) were distributed homogeneously through the PI matrix. The effect of the titania content in the PI on DC conductivity and dielectric constant were also analyzed. For the PI film containing 5 wt % titania, activation energy value increased to 1.0 eV from the value of 0.65 eV. DC conductivity value of the films depending on titania content varied between 3.0 × 10⁻¹¹ and 1.4 × 10⁻¹⁰ S/cm at room temperature. Relative dielectric constants of the films were calculated from capacitance measurements depending on frequency (40–100 kHz) at different temperatures (303–360 K). The values increased with the increasing titania content. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

丙烯酸树脂/TiO2有机-无机杂化材料的表面性质研究

采用预水解的二氧化钛（TiO2)溶胶与丙烯酸树脂共混或原位聚合的方法成功地制备了均匀透明的丙烯酸树脂／TiO2有机—无机杂化材料。通过原子力显徽镜(AFM)、X-射线光电子能谱(XPS)和表面接触角研究了杂化材料涂层的表面性质。结果发现在杂化材料中添加TiO2后，涂层的表面粗糙度、表面Ti元素含量和表面自由能增加，接触角下降。     

Atomic oxygen erosion resistance of titania–polyimide hybrid films derived from titanium tetrabutoxide and polyamic acid

A series of polyimide/titania (PI/TiO₂) hybrid films have been successfully synthesized based on titanium tetrabutoxide (Ti(OEt)₄), 3,3′,4,4′‐bezonphenone tetracarboxylic dianhydride (BTDA), 4,4′‐oxydianiline (ODA), and 1,3‐bis(aminopropyl) tetramethyldisiloxane (APrTMOS) by a sol–gel process. The atomic oxygen (AO) exposure tests were carried out using a ground‐based AO effects simulation facility. The chemical structure of PI/TiO₂ films was characterized by Fourier transform‐infrared (FT‐IR) spectroscope before and after AO exposure. The glass transition temperature (T_g) and mechanical properties were examined by dynamic mechanical analysis (DMA) and universal mechanical testing machine, respectively. The tensile strength and elongation of the hybrid film decreased with the increase of TiO₂ content, whereas the T_g increased with the increase of TiO₂ content. The effects of TiO₂ content on the morphology and structure evolvement of PI/TiO₂ hybrid films were also investigated using field emission scanning electron microscopy (FE‐SEM) and X‐ray photoelectron spectroscope (XPS), respectively. The results indicated that a TiO₂‐rich layer resulting from the Ti(OEt)₄ formed on the PI film after AO exposure, which decreased the mass loss rate and obviously improved the AO resistance of PI films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Novel organic-inorganic hybrids prepared from polybenzoxazine and titania using sol-gel process

Novel organic-inorganic hybrids were prepared from polybenzoxazine and titania using sol-gel process by blending titanium isopropoxide as a precursor for titania with a typical benzoxazine monomer, bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl)isopropane (Ba). Deep red brown and transparent hybrid materials were obtained after thermal cure at 200 °C. DSC indicated that, in the presence of titania precursor, the onset and maximum temperature of the exothermic peak due to the ring opening polymerization of Ba decreased by ca. 30 and 70 °C, respectively. Viscoelastic analyses revealed that the glass transition temperatures (T_g) of the polybenzoxazine-titania hybrids shifted to higher temperature than the neat polybenzoxazine. The storage moduli below T_g for the hybrids increased with the increase of the titania content, and the storage moduli were maintained constant up to higher temperature than the neat resin. TGA results confirmed that the thermal stability and char yield of polybenzoxazine increased by hybridization with titania.     

溶胶-凝胶法制备聚丙烯酸酯/纳米TiO2有机-无机杂化材料的研究

以丙烯酸酯单体为原料,采用常规溶液聚合法制备了聚丙烯酸酯溶液,以钛酸正丁酯为前驱体,水解制备纳米二氧化钛溶胶,两者在常温高剪切力下共混,制得聚丙烯酸酯/纳米TiO2有机-无机杂化材料。分别用透射电子显微镜(TEM),原子力显微镜(AFM),双光束紫外-可见分光光度计UV-VIS,热重分析(TGA),拉伸测试研究了纳米溶胶以及杂化材料的性能。结果表明:TiO2在溶胶和杂化材料中都呈纳米级均匀分散,而且杂化材料的光学,热学,力学性能都比纯聚丙烯酸酯有显著的提高。     

Mechanically stable flat anodic titania membranes for gas transport applications

Anodic titanium oxide (ATO) membranes were produced by two-step anodic oxidation of titanium foil in ethylene glycol electrolyte containing NH₄F at the anodization voltage of 60?V. To provide the mechanical strength necessary for applying tubular anodic films as gas membranes, we utilized the formation of protective continuous TiO₂ layer at the top film surface prior to second anodization. As compared to conventional two-step anodic oxidation this technique decreases dissolution rates of titanium oxide phases with oxidation states lower than +4 (Ti₂O₃, Ti₃O₅), which are forming between titania nanotubes during anodization. The structural parameters of anodic titania films were determined by small-angle X-ray scattering and scanning electron microscopy techniques. According to SEM the proposed method resulted in growth of ATO films with a flat surface without nanotube endings, which enabled to use the films as gas separation membranes. The permeance of individual gases through ATO membranes were found to depend on gas molecular weight (M^?0.5), with absolute values twice exceeding theoretical permeabilities as it was predicted by Knudsen diffusion (up to 63?m³/(m²?×?bar?×?h) for nitrogen at 298?K). Here we ascribe this phenomenon to diffusion according to Knudsen-Smoluchoski mechanism (diffusion with slip, involving specular reflections of molecules), which is appropriate for membranes with straight pores and smooth internal pore surfaces.     

Effect of TiO2 on thermal and adhesive characteristics of poly(imide siloxane)/TiO2 hybrid films

A novel poly(imide siloxane)/titania (PIS/TiO₂) hybrid film was fabricated by sol‐gel process via in situ formation of TiO₂ within PIS matrix. Poly(amic acid siloxane) (PAAS) was prepared from 4,4′‐oxydiphthalic anhydride, 2,2‐bis [4‐(4‐aminophenoxy) phenyl] propane, and α,ω‐bis(3‐aminopropyl)polydimethylsiloxane (APPS). Chelating agent, acetylacetone, and catalyst‐free polymerization were used to reduce the rate of hydrolysis of titanium alkoxide in the PAAS. X‐ray photoelectron spectroscopy data showed that the presence of APPS promotes the Ti surface composition of PIS/TiO₂ hybrid film. The effects of TiO₂ and APPS contents on the characteristics of surface, thermostability, coefficient of thermal expansion (CTE), and the strength of adhesion were investigated. The presence of TiO₂ on the surface of the hybrid films enhanced the adhesive strength at the interface of PIS/TiO₂ hybrid film and copper foil. When more TiO₂ was incorporated into the PIS matrix, the PIS/TiO₂ hybrid film exhibited lower CTE while retaining favorable mechanical and thermal properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,structural characterization and properties of novel functional poly(ether imide)/titania nanocomposite thin films

In this study, the synthesis, morphology, and thermal properties of new poly(ether imide)/titania nanohybrid films were investigated. The novel diamine containing functional nitrile groups was prepared in two steps by the nucleophilic substitution reaction and it was fully characterized by different techniques. Reaction of this diamine with pyromellitic dianhydride and 4-aminobenzoic acid gave poly(ether imide) with carboxylic acid end groups. This acid functionalized poly(ether imide) was condense with different amount of TiO₂ nanoparticles to provide organic-inorganic bonding, and the flexible films of these hybrid were prepared. The obtained materials were characterized by Fourier transform-infrared spectroscopy, thermogravimetry analysis (TGA), differential scanning calorimetry, X-ray powder diffraction, UV–Vis spectroscopy, field emission-scanning electron microscopy, and transmission electron microscopy (TEM) techniques. TEM of the nanohybrid films with 12% of TiO₂ contents confirms well dispersion of nanoparticles in the polymer matrix. TGA data indicated that the thermal behavior of the hybrid materials was increased with an increasing the content of TiO₂ nanoparticles. The tensile stress–strain of the hybrids was investigated and the resulting nanocomposites showed good mechanical properties. The permeability and selectivity of the PEI/TiO₂ membranes as a function of the titania weight percentage were study and the results indicated that the permeabilities of CO₂ and N₂ increase with increasing the titania content.     

Study on acrylic resin/titania organic-inorganic hybrid materials prepared by the sol-gel process

Acrylic resin/titania organic-inorganic hybrid materials were prepared by the two approaches. One approach (BL method) was blending titania produced by the sol-gel process with synthesized acrylic resins containing various content of acrylic acid (AA). Another approach (IS method) was the in situ polymerization of acrylic monomers in synthesized titania sols. The structure and mechanical, thermal and optical properties of the hybrid films were investigated by small angle X-ray scattering (SAXS), atomic force microscopy (AFM), dynamic mechanical analysis (DMA), Instron testing machine, thermogravimetric analysis (TGA) and ultraviolet-visible spectroscopy (UV-VIS), respectively. Titania phase in the hybrids showed an open structure and nano-scale size. However, aggregation of titania occurred in the systems prepared by IS method or without AA contained. The mechanical properties, thermal stability and UV shielding properties of organic polymer were obviously improved with titania networks embedded. It was found that BL method could prepare homogeneous hybrids with better integrative mechanical properties in comparison with IS method.     

Water absorption characteristics of hybrid materials incorporating tetrabutyl titanate with acrylic polymer via sol–gel process

The sol–gel process was used to prepare organic/inorganic hybrids utilizing a terpolymer of n‐butyl methacrylate, methyl methacrylate, and methacrylic acid as an organic phase and titanium tetrabutoxide as a precursor of the inorganic phase. Such hybrid materials may be of interest as primers for corrosion protection of metal substrates. In the absence of electrochemical influence, which is usually provided by anticorrosive pigments in current protective coatings, the barrier mechanism becomes one of the basic elements for protecting metals against atmospheric corrosion. In that context, we report the water uptake characteristics of hybrid films with titania content up to 16.3 wt %. The slow hydrolysis of butoxy, acetate, and carboxylate ligands, which becomes more and more obvious with an increase in titanium oxide cluster content, is found to produce a chemically driven force for water uptake in hybrids. The 4.6 wt % TiO₂ hybrid results in the best balance of properties with a far lower diffusion coefficient and nearly the same amount of water absorbed at saturation compared to the polymer matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 92–102, 2005     

Photo‐differential scanning calorimetry study on photopolymerization of nanosized titanium dioxide/polyacrylate hybrid materials

Nanosized titania–polyacrylate hybrid films were prepared by controlled hydrolysis of titanium tetrabutoxide (TTB) in Span 85/Tween 80 reverse micelles as well as rapid entrapment of nanosized particles by subsequent photopolymerization. This work focused on the characterization of the photopolymerization of the transparent hybrid films via photocalorimetry. The polymerization kinetics of several mixtures of mono‐ and di‐functional acrylate monomers were compared to examine the effect of average functionality. Further, Effects of [H₂O]/[surfactant] molar value and TTB concentration on photopolymerization kinetics were also studied. X‐ray photoelectron spectra and FTIR demonstrated the formation of TiO₂ in the hybrid films. Atomic Force Microscope (AFM) images showed the inorganic domains with mean sizes of 25 nm were uniformly dispersed in the polymeric networks. Copyright © 2006 Society of Chemical Industry     

Polyimide/nano-TiO2 hybrid films having benzoxazole pendent groups: In situ sol–gel preparation and evaluation of properties

Polyimide/titania (PI/TiO₂) nanocomposite films have been successfully fabricated through the in situ formation of TiO₂ within a PI matrix via sol–gel method. Poly(amic acid) (PAA), which is the precursor of PI, was successfully synthesized by mixing pyromellitic dianhydride (PMDA), with equimolar amount of a diamine monomer having a pendent benzoxazole unit and two flexible ether linkages in N,N-dimethylformamide (DMF) solvent. Tetraethyl orthotitanate [Ti(OEt)₄] and acetylacetone were then added to the resulted PAA. After imidization at high temperature, PI/TiO₂ hybrid films were formed. The structure and morphology of the hybrid nanocomposites with different titania contents (0 wt%, 5 wt%, 10 wt%, and 15 wt%) were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The results indicate that the TiO₂ nanoparticles were homogeneously dispersed in the hybrid films. The thermogravimetric analysis of nanocomposites confirms the improvement in the thermal stability with the increase in the percentage of titania nanoparticle. Transmission electron microscopy showed that the nanoparticles with an average diameter of 25–40 nm were dispersed in the polymer matrix.     

Preparation and properties of polyimide films codoped with barium and titanium oxides

Polyimide hybrid films containing bimetalic compounds were obtained by codoping poly(amic acid) with a barium and titanium precursor prepared from BaCO₃, Ti(OBu)₄, and lactic acid followed by casting and thermal curing. FTIR, WAXD, and XPS measurements showed that barium and titanium precursor could be transformed to BaTiO₃ at a temperature above 650°C, while the mixed oxides were only found in hybrid films. The measurements of TEM and AFM indicated a homogeneous distribution of inorganic phase with particle sizes less than 50 nm. The hybrid films exhibited fairly high thermal stability, good optical transparency, and promising mechanical properties. The incorporation of 10 wt % barium and titanium oxide lowered surface and volume electrical resistivity by 2 and 5 orders, respectively, increasing dielectric constant from 3.5 to 4.2 and piezoelectric constant from 3.8 to 5.2 × 10^?12 c/N, relative to the nondoped polyimide film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1810–1816, 2002     

Fabrication of a New Polyimide/Titania (TiO2) Nanocomposite Thin Film by the Sol-Gel Route

Polyimide/titania nanocomposite (PI/TiO₂ NC) was successfully fabricated through the in situ formation of TiO₂ within a PI matrix by the sol-gel process. FT-IR and XRD results confirmed the formations of the TiO₂ in the PI matrix. Transmission electron microscopy of the NC10% showed that the TiO₂ phase was well dispersed in the polymer matrix. The mechanical properties of the NC films were increased and elongation at break decreased with increasing TiO₂ content. Thermogravimetric analysis results revealed that the decomposition temperature of hybrid materials was increased with an increase in the content of TiO₂ nanoparticles within the NC films.     

Microstructure and properties of polyimide/poly(vinylsilsesquioxane) hybrid composite films

Polyimide (PI)/poly(vinylsilsesquioxane) (PVSSQ) (PI/PVSSQ) hybrid composite films were prepared from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA)-4,4′-oxydianiline (ODA) polyamic acid and triethoxyvinylsilane (TEVS or VSSQ) via sol-gel process and thermal imidization. The presence of the PVSSQ showed a remarkable effect on the microstructure and properties of the polyimide based hybrid films. The transparency of the hybrid films decreased with increasing the content of the PVSSQ. The compatibility and interfacial interaction of the hybrid composites were evaluated by scanning electron microscope (SEM) and atomic force microscope (AFM), respectively. The PI/PVSSQ hybrids showed nanocomposite formation when the contents of PVSSQ was less than 20 wt%. It was found that the surface topography was influenced by the composition of the PVSSQ. Incorporating of the PVSSQ increased the thermal stability and T_g of hybrid composites. The dielectric constant of the hybrid composites was reduced by adding PVSSQ up to a certain content, showed a minimum and then found to be increased. The dielectric constant values of the hybrid composites ranged from 2.59 to 3.78. The presence of the PVSSQ also showed significant effects on the mechanical properties of the polyimide films.     

Preparation and characteristics of polyimide–TiO2 nanocomposite film

A sol–gel approach has been developed to prepare polyimide–TiO₂ hybrid films from soluble polyimides and a modified titanium precursor. The rate of the hydrolysis reaction of titanium alkoxide can be controlled by using acetic acid as a modifier. FTIR and XPS indicated that TiO₂ particles were well distributed in polyimide matrixes with particle size small per than 60 nm. Polyimide hybrid films having the TiO₂ component ≤10% exhibited high thermal stability, high optical transparency and good mechanical properties and possessed higher dielectric constants than correspondingly polyimides. © 2000 Society of Chemical Industry