Preparation and barrier property of poly(vinyl alcohol)/SiO<Subscript>2</Subscript> hybrid coating films

Using sol-gel method, poly(vinyl alcohol)/SiO₂ hybrid coating materials with an improved gas barrier property could be produced. Phase compatibility between organic PVA segments and inorganic silicate network in the hybrid was evaluated by analyzing FT-IR spectra and investigating the crystallization behavior in terms of X-ray diffraction patterns for the hybrid gels. For the preparation of coating film with barrier property, the biaxially oriented polypropylene (BOPP) substrate was coated with the hybrid sols by a spin coating method. Morphological analysis for the fractured surface of the hybrid gel and the surface of the coated film was performed not only to examine the microstructure of the hybrid, but also to propose evidence for the oxygen permeation behavior through the coated film. It was revealed that an optimum amount of inorganic silicate precursor, TEOS, should be used to obtain high barrier PVA/SiO₂ hybrid coating materials with enhanced micro-phase morphology and optical transparency. This homogeneous morphology densified with nano-structured silicate, obtained at optimal conditions, was found to result in a significant increase in the oxygen barrier property of film coated with PVA/SiO₂ hybrid by about 50 times relative to the pure BOPP substrate. In addition, the effect of pretreatments of the BOPP substrate surface on the barrier property was also examined.     

Preparation,Characterization, and Properties of Novel Polyimide–SiO2 Hybrid Composites Based on Bipyridine for Low Dielectric Applications

Novel low dielectric polyimide–SiO₂ hybrid materials containing bipyridine were prepared with three-step sol–gel process from poly(amic acid)s. (3-Aminopropyl)triethoxysilane as coupling agent was used to increase the intrachain chemical bonding between the polyimide and SiO₂ groups. The thermal, dielectric, and physical properties of the hybrid materials were investigated and correlated with the porous structure. The glass transition temperatures of all the hybrids were found to be higher than polyimides. The effect of SiO₂ groups on the porous structure and dielectric properties was investigated. The dielectric constant of the hybrid materials was observed a decrease from 3.30 to 2.15 with increased SiO₂ amount.     

Synthesis and characterization of titanium dioxide optical films by sol–gel processes

The main purpose of this study is to synthesize the front panel of monitor with a high refractive index optical film. Our experiment uses titanium dioxide nanoparticles mixed with methyl methacrylate (MMA), 2‐hydroxyethyl methacrylate (2‐HEMA), and tri(ethylene glycol) dimethacrylate (TEGDMA) of the wet type and economical sol–gel production process. Our product has a superior mechanical, thermal, and optical properties was demonstrated by Fourier transform infrared spectrum (FTIR), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), UV/visible spectrum, and Spectro Ellipsometer. In addition, we found the surface of the two series of thin film with the organic and inorganic high refractive index (TiO₂) mixed materials, has high transmittance for visible light above 90%, refractive index <1.65 and the hardness test 6H. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2271–2280, 2007     

改性纳米SiO2/聚氨酯-含氟丙烯酸酯无皂乳液合成及其胶膜性能表征

引言水性聚氨酯相对溶剂型聚氨酯具有不燃、气味小、不污染环境等优点[1-2],从而广泛用于涂料[3]、胶黏剂[4]、油墨[5]等领域。目前,常用于软包装领域的薄膜主要是表面能很低的非极性膜,而水性聚氨酯胶黏剂具有较高的表面自由能,对非极性膜的润湿性差,因此需要降低水性聚氨酯的表面张力,达到润湿非极性膜的目的。     

Preparation,characterization, and properties of environmentally friendly waterborne poly(urethane acrylate)/silica hybrids

A series of environmentally friendly waterborne poly(urethane acrylate) (WPUA)/silica (SiO₂) hybrids were synthesized by a sol–gel process on the basis of isophorone diisocyanate, polyester polyol (GE‐210), dimethylpropionic acid, butyl acrylate and methyl methacrylate monomers, tetraethoxysilane (TEOS), and 3‐glycidyloxypropyl trimethoxysilane (GLYMO) as a coupling agent. The mechanical properties of the WPUA/SiO₂ hybrids were investigated through tensile and hardness tests. Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and X‐ray diffraction were used to assess the fracture surface morphology and the dispersions of the WPUA/SiO₂ hybrids. The strength and hardness values of the WPUA/SiO₂ hybrids were improved significantly. This was attributed to the synergistic effect of WPUA, GLYMO, and TEOS. The results show that SiO₂ particles of the membranes had a uniform dispersion and formed an excellent interfacial bonding layer on their surfaces. The prepared hybrids showed good thermal stability and mechanical properties in comparison with pure WPUA and showed tunable transparence with the SiO₂ fraction in the film. Through suitable adjustment of the TEOS content, some thin hybrids have potential applications as specialty materials. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation, characterization and properties of UV-curable waterborne polyurethane acrylate/SiO2 coating

The UV-curable waterborne polyurethane acrylate (UV-WPUA) oligomer was first prepared based on isophorone diisocyanate (IPDI), polyether polyol (NJ-220), dimethylol propionic acid (DMPA), and hydroxyethyl methyl acrylate (HEMA) via an in situ method. With the different content tetraethoxysilane (TEOS) and 3-glycidyloxypropyltrimethoxysilane (GLYMO) as coupling agents, a series of waterborne UV-WPUA/SiO₂ oligomers were prepared by the sol?Cgel process. The physical and mechanical properties of the UV-WPUA and UV-WPUA/SiO₂ hybrid coating materials were measured. The UV-WPUA and WPUA/SiO₂ hybrid materials were characterized using FTIR spectra, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD) measuring apparatuses to determine their structures, thermal properties, surface morphologies, etc. The results showed the SiO₂ particles of the hybrid materials had wide dispersion, forming a good interfacial bonding layer on surfaces. The tensile strength, water resistance, and thermal properties of the hybrid materials were better than those of the UV-WPUA. The resulting UV-WPUA/SiO₂ hybrids are promising for a number of applications, e.g., for high-performance water-based UV-curable coatings.     

Towards facile fabrication of photonics components from inorganic and hybrid sol-gel films. Preparation and optical properties characterization

New trends towards development of integrated optics and miniaturization of photonic devices require fabrication of miniaturized photonic components. Fabrication of waveguiding films with designed optical properties is a fundamental process for production of planar integrated devices.We report here preparation of thin layers based on TiO₂ precursor (TET – titanium(IV) ethoxide) and SiO₂ precursors, namely inorganic (TEOS – tetraethyl orthosilicate) or organically modified (GLYMO ? 3-glycidoxypropyltrimethoxysilane) as candidates for potential application in the planar integrated circuits.The thin layers were deposited on soda-lime glass substrates using the sol-gel method and dip-coating technique and processed at relatively low temperature (up to 300 °C). Several parameters e.g. a) the type of SiO₂ precursor, b) the presence of complexing agent for TET and c) heat treatment temperature were tested for their influence on thickness and refractive index of the obtained films.Furthermore, a few series of sol-gel films activated with luminescent dye (Rhodamine B) was fabricated. The influence of the above-listed parameters on luminescent properties of the films was characterized because of lack of systematic study in the literature in this aspect. Moreover, a spectrum of the light at the output of a chosen luminescent dye-doped waveguiding film excited by laser source was investigated.In addition, the subject of our investigations were films prepared at 200 °C with various amounts of TET and organically modified SiO₂ precursor in concentration range not presented before. Their optical properties such as homogeneity and values of optical band gap of TiO₂ clusters were explored. For selected samples the waveguide properties including the optical losses were evaluated. For the first time, hybrid films with presented composition and refractive index in range of 1.59–1.71 were used for patterning by nanoimprint technique allowing for reproduction of periodic structures, which may serve for example as grating couplers or DFB (distributed feedback) resonators.     

Preparation and Properties of Water-Soluble PAA–PAS/SiO2 Hybrid Materials

Copolymers with different weight ratios of AA/PAS (acrylic acid/poly(DL-aspartic acid)) were synthesized and blended with sol-gel precursors to prepare water-soluble PAA–PAS/SiO₂ inorganic/organic hybrid materials. The PAS polymer or its copolymer in PAA–PAS/SiO₂ formed hydrogen bonds with SiO₂ and the amorphous structure of the hybrid material varied with the weight ratio of PAA. The hybrid materials exhibited enhanced thermal resistance over the copolymer alone. All hybrid materials were water-soluble and relatively insoluble in organic solvents.     

Thermal stability and abrasion resistance of polyacrylate/nano-silica hybrid coatings

Polyacrylate (PAE)/nano-silica (SiO₂) hybrids were prepared by an in situ sol–gel process of tetraethyl orthosilicate in the presence of PAE toluene solution. The hybrid coatings were fabricated using a PAE/SiO₂ suspension by the traditional casting. Their intermolecular interaction and morphology, as well as thermal, mechanical, and optical properties, were investigated using Fourier transform infrared spectroscopy, field-emission scanning electron microscope, differential scanning calorimetry and TG/DTA thermogravimetric analysis, coating impact testing, and UV–Vis spectroscopy, respectively. At the same time, their abrasive properties were carried out by abrasion resistance and nanoindentation tests. The results indicate that silica nanoparticles, with diameter about 30 nm, can disperse homogeneously in the PAE matrix, where hydrogen bonds between the PAE and nano-silica are formed. Therefore, homogeneous dispersion of nano-silica particles provides high transparency for the PAE/SiO₂ hybrid coating as the size of nano-silica phase is much smaller than the wavelength (390–770 nm) of visible light. PAE/nano-silica hybrid coatings have increased T _g and thermal stability including the onset decomposition temperature, 10 % weight loss temperature, and char at 700 °C. Additionally, the incorporation of nano-silica particles improves the glossiness of the PAE/nano-silica hybrid coatings and enhances their abrasion resistance and surface hardness. The nano-silica content has obvious effect on the thermal, mechanical, optical, and anti-abrasion properties of PAE/SiO₂ hybrid coatings. With the consideration of all the properties of hybrid coatings, the PAE/SiO₂ hybrid containing 10 phr of nano-silica has the optimal composition. These PAE/nano-silica hybrid coatings have potential applications in high-performance hologram image recording.     

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.     

Phase compatibility and barrier properties of ethylene/vinyl alcohol copolymer based hybrid materials

An ethylene/vinyl alcohol copolymer (EVOH) with superior barrier properties was used as an organic component to prepare EVOH/SiO₂ hybrid materials with improved gas barrier properties with a sol–gel method. As a silane coupling agent, 3‐isocyanatopropyl triethoxysilane (IPTES) was used to promote interfacial attraction between the organic EVOH segments and the inorganic silicate network in the hybrid. The phase compatibility was evaluated by analysis of Fourier transform infrared spectroscopy and phase morphology and the optical properties of the hybrids. We confirmed that the addition of the silane coupling agent IPTES up to some level of content resulted in enhanced phase compatibility and optical transparency of the nanostructured hybrid material with a homogeneous phase morphology exhibiting no microphase separation. For the preparation of the monolayer coated film, the biaxially oriented polypropylene substrate pretreated with a corona was coated with the hybrid sols by a spin‐coating method. The oxygen permeation behavior through the coated film was examined with various contents of the silane coupling agent IPTES and inorganic silicate precursor tetraethoxyorthosilicate in the hybrid system. Consequently, it was revealed that an optimum range of IPTES and tetraethoxyorthosilicate contents was required to produce high barrier EVOH/SiO₂ hybrid materials with a stable homogeneous microstructure and enhanced optical transparency. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of modified SiO2 networks: Polydimethylsiloxane-SiO2 organic-inorganic hybrids via sol-gel chemistry

Poly(dimethylsiloxane)-SiO₂ organic-inorganic hybrid networks were synthesized by a two-step, catalyst-free sol-gel process. Reactive PSX (polydimethylsiloxane) oligomers with methoxysilyl end-groups were used as the organic component, and tetramethylorthosilicate (TMOS) as the inorganic component of the hybrid. Our studies show that uncatalyzed sol-gel reactions based on TMOS can reach gelation in 7.5 h when reacted at room temperature, with a stoichiometric amount of water necessary for complete hydrolysis in the initial stages, and at a high concentration of reacting species. The relatively neutral reaction environment of this catalyst-free process is important in the synthesis of PSX-SiO₂ hybrid networks because it prevents redistribution reactions of PSX modifiers, especially when higher temperatures are used for the drying of the gels. The PSX-SiO₂ hybrid networks have reduced polarity, increased water resistance, and improved toughness compared to inorganic SiO₂ networks produced under similar conditions.     

Preparation,Morphology and Properties of Waterborne-Polyurethane/Silica

A series of waterborne-polyurethane/silica (WPU/SiO₂) were prepared from isophoronediisocyanate, polyester polyol, dimethylolpropionic acid, tetraethoxysilane and 3-glycidyloxypropyl trimethoxysilane. The WPU/SiO₂ dispersion had narrower particle size distribution than the pure WPU. The mechanical properties of WPU/SiO₂ films were improved than the pure WPU. WPU/SiO₂ films were characterized by FT-IR spectroscopy, SEM, TEM, AFM, XRD and UV-Vis spectroscopy. The results showed that WPU/ SiO₂ hybrid films were found to be smooth morphology, and had good thermal stability and tunable transparence with the silica fraction in the film. Through suitable adjustment of silica content, some thin films have potential applications as the specialty materials.     

Organic‐acid‐catalyzed sol–gel route for preparing poly(methyl methacrylate)–silica hybrid materials

In this study, a series of organic–inorganic hybrid sol–gel materials consisting of a poly(methyl methacrylate) (PMMA) matrix and dispersed silica (SiO₂) particles were successfully prepared through an organic‐acid‐catalyzed sol–gel route with N‐methyl‐2‐pyrrolidone as the mixing solvent. The as‐synthesized PMMA–SiO₂ nanocomposites were subsequently characterized with Fourier transform infrared spectroscopy and transmission electron microscopy. The solid phase of organic camphor sulfonic acid was employed to catalyze the hydrolysis and condensation (i.e., sol–gel reactions) of tetraethyl orthosilicate in the PMMA matrix. The formation of the hybrid membranes was beneficial for the physical properties at low SiO₂ loadings, especially for enhanced mechanical strength and gas barrier properties, in comparison with the neat PMMA. The effects of material composition on the thermal stability, thermal conductivity, mechanical strength, molecular permeability, optical clarity, and surface morphology of the as‐prepared hybrid PMMA–SiO₂ nanocomposites in the form of membranes were investigated with thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, gas permeability analysis, ultraviolet–visible transmission spectroscopy, and atomic force microscopy, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The situ preparation of silica nanoparticles on the surface of functionalized graphene nanoplatelets

A method for situ preparing a hybrid material consisting of silica nanoparticles (SiO₂) attached onto the surface of functionalized graphene nanoplatelets (f-GNPs) is proposed. Firstly, polyacrylic acid (PAA) was grafted to the surface of f-GNPs to increase reacting sites, and then 3-aminopropyltriethoxysilane (APTES) KH550 reacted with abovementioned product PAA-GNPs to obtain siloxane-GNPs, thus providing reaction sites for the growth of SiO₂ on the surface of GNPs. Finally, the SiO₂/graphene nanoplatelets (SiO₂/GNPs) hybrid material is obtained through introducing siloxane-GNPs into a solution of tetraethyl orthosilicate, ammonia and ethanol for hours'' reaction. The results from Fourier transform infrared spectroscopy (FTIR) showed that SiO₂ particles have situ grown on the surface of GNPs through chemical bonds as Si-O-Si. And the nanostructure of hybrid materials was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). All the images indicated that SiO₂ particles with similar sizes were grafted on the surface of graphene nanoplatelets successfully. And TEM images also showed the whole growth process of SiO₂ particles on the surface of graphene as time grows. Moreover, TGA traces suggested the SiO₂/GNPs hybrid material had stable thermal stability. And at 900°C, the residual weight fraction of polymer on siloxane-GNPs was about 94.2% and that of SiO₂ particles on hybrid materials was about 75.0%. However, the result of Raman spectroscopy showed that carbon atoms of graphene nanoplatelets became much more disordered, due to the destroyed carbon domains during the process of chemical drafting. Through orthogonal experiments, hybrid materials with various sizes of SiO₂ particles were prepared, thus achieving the particle sizes controllable. And the factors’ level of significance is as follows: the quantity of ammonia > the quantity of tetraethyl orthosilicate (TEOS) > the reaction time.     

High-temperature mechanical properties of NextelTM 610 fiber reinforced silica matrix composites

Novel Nextel? 610 fiber reinforced silica (N610f/SiO₂) composites were fabricated via sol-gel process at a sintering temperature range of 800–1200?°C. The sintering-temperature dependent microstructures and mechanical properties of the N610f/SiO₂ composites were investigated comprehensively by X-ray diffraction, nanoindentation, three-point bending etc. The results suggested a thermally stable Nextel? 610 fiber whose properties were barely degraded after the harsh sol-gel process. A phase transition in the silica matrix was observed at a critical sintering temperature of 1200?°C, which led to a significant increase in the Young's modulus and hardness. Due to the weak fiber/matrix interfacial interaction, the 800?°C and 1000?°C fabricated N610f/SiO₂ composites exhibited quasi-ductile fracture behaviors. Specially, the latter possessed the highest flexural strength of ≈ 164.5?MPa among current SiO₂-matrix composites reinforced by fibers. The higher sintering-temperature at 1200?°C intensified the SiO₂ matrix, but strengthened the interface, thus resulting in a brittle fracture behavior of the N610f/SiO₂ composite. Finally, the mechanical properties of this novel composite presented good thermal stability at high temperatures up to 1000?°C.     

Characterization of poly(2-hydroxyethyl methacrylate-silica) hybrid materials with different silica contents

Poly(2-hydroxyethyl methacrylate-silica) hybrid materials with significantly lower volume shrinkage were synthesized by using acid-catalyzed sol-gel reactions of tetraethyl orthosilicate and free radical polymerization of 2-hydroxyethyl methacrylate (HEMA). The mechanical, thermal, and optical properties and internal porosities of the poly(HEMA-silica) hybrids with different silica contents (e.g., 15, 25 and 30 wt%) were evaluated with the use of nanoindentation, microscratch, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, UV-vis spectrophotometer and N₂ adsorption-desorption method. A silica percolation threshold was found at around 20-25 wt%, beyond which a marked increase in the poly(HEMA-silica) hybrid hardness and modulus was observed as compared to pure poly(HEMA). Nanoindentation and scratch testing measurements also for the first time were introduced in characterizing poly(HEMA-silica) hybrid materials.     

Characterization and properties of UV‐curable polyurethane‐acrylate/silica hybrid materials prepared by the sol‐gel process

UV‐curable, transparent hybrid material of urethane‐acrylate resin was prepared by the sol‐gel process using 3‐(trimethoxysilyl)propylmethacrylate (TMSPM) as a coupling agent between the organic and inorganic phases. The effects of the content of acid and silica on the morphology and mechanical properties of UV‐curable polyurethane‐acrylate/silica hybrid (UA‐TMSPM)/SiO₂ materials have been studied. The results of thermogravimetric analysis for the (UA‐TMSPM)/SiO₂ hybrid materials indicated that the thermal stability of the hybrids is greatly improved. It was found that with the increase of HCl content, the interfacial interaction between organic and inorganic phases had been strengthened, as demonstrated by field emission scanning electron microscopy. Without sacrificing flexibility, the hybrid materials showed improved hardness with increasing content of acid and silica. Compared with the pure organic counterpart UA/hexanediol diacrylate (UA/HDDA) system, abrasion resistance of the hybrids improved with increasing acid content, at low silica content. Copyright © 2004 Society of Chemical Industry     

The synthesis of carbon nanotube based composites with conducting, semiconducting, and insulating coatings and their optical limiting properties

Multiwalled carbon nanotubes (MWCNTs) were individually coated with conducting, semiconducting, and insulating materials. The coatings used were crystalline Au nanoparticles, TiO₂ nanoclusters, and amorphous SiO₂ nanoshells, respectively. The synthesis strategy involves a combination of self-assembly and the sol-gel technique. The synthesized nanostructures were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction. We investigated the nonlinear optical and optical limiting properties using an open-aperture Z-scan technique and fluence-dependent transmittance measurements. Compared to the pristine MWCNTs, those with Au-, TiO₂-, and SiO₂-coatings demonstrate superior, equivalent, and inferior nonlinear optical and optical limiting properties, respectively.     

One-step synthesis of improved silica/epoxy nanocomposites with inorganic-organic hybrid network

High performance silica/epoxy nanocomposites were prepared through mixing epoxy, tetraethyl orthosilicate (TEOS), γ-aminoproplytriethyoxy siliane(APTES), and triethyltrtramine (TETA) at 25 °C via sol-gel method on one-step. The effects of content of TEOS and coupling reagents on the mechanical and thermal properties of SiO₂/EP composites were studied. Microcosmic morphology and properties of the hybrid materials were characterized by FT-IR, TEM, FESEM, and DSC. Results revealed that SiO₂/EP composites achieve the optimal mechanical and thermal properties when the composites prepared with mass ratio of TEOS/APTES/epoxy for 3/2/100 without acetone. Compared with pristine epoxy, the tensile strength, elongation at break, impact strength and bend strength increased 67.6 %, 190 %, 82.1 % and 15.7 %, respectively. The further study was to investigate the content of TEOS and APTES effecting on mechanical properties and water sorption of fiber reinforced composites, which used the above compound as matrix resin.