Structure and surface properties of fluorinated organic–inorganic hybrid films

Fluorinated organic–inorganic hybrid films were prepared by sol–gel process from tridecafluoroctyltriethoxysilane (PFAS), 3-glycidoxypropyltrimethoxysilane, and tetraethoxysilane (TEOS). It has been found that the fluorinated hybrid films possessed fluorinated side chains originating from PFAS as top layer, and silica network as bottom layer, which had very low surface energy and could be used as water repellent functional coatings. The outermost layer of the water-repellent film may be fully covered by the perfluoroalkyl side chains as the molar ratio of PFAS/TEOS increases up to about 0.005:1. The addition of BPA can enhance the cross-link density of fluorinated hybrid films, and make more perfluoroalkyl groups enriching at the coating film-air interface to lower the surface free energy. However, the improvement of the cross-link density of fluorinated hybrid films tends to exhibit brittleness and micro-cracks. Consequently, it can be concluded that a small BPA additive content is preferred for the formation of fluorinated hybrid films with a smooth surface and less detectable cracks.     

Synthesis and properties of organic–inorganic hybrid liquid crystal gels

Organic–inorganic hybrid liquid crystal (LC) gels have been synthesised by the thiol-ene reaction of a multifunctional cyclic siloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (TVMCTS) and alkane dithiols, 1,6-hexanedithiol (HDT) or 1,9-decanedithiol (DDT), in LC matrices, 4-cyano-4?-pentylbiphenyl (5CB) or 4′-n-octyl-4-cyano-biphenyl (8CB). The LC gels were prepared in an isotropic phase at 70°C or mesophases at 25°C using radical initiators. The phase transition temperatures from a mesophase to an isotropic phase of the resulting gels were lower than those of the original LCs. The gels containing 8CB (8CB gels) prepared at 25°C showed two phase transitions: smectic-to-nematic and nematic-to-isotropic transitions. By contrast, the 8CB gels synthesised in the isotropic phase showed only one phase transition from smectic phase directly to isotropic phase. Reaction conversions in the LC gels prepared at 70°C were higher than that in the gels prepared at 25°C. Scanning microscopic light scattering analysis of the LC gels cleared homogeneous small size mesh with a small amount of large defect. Polarisation micrographs of the LC gels showed framed optical textures derived from the LC molecules at room temperature. The LC gels containing more than 90 wt% of LC showed electro-optic response.     

Elastic organic–inorganic hybrid aerogels and xerogels

Novel aerogels and xerogels with methylsilsesquioxane (MSQ, CH₃SiO_1.5) networks have been prepared by a modified sol–gel process using surfactant and urea as a phase-separation inhibitor and as an accelerator for the condensation reaction, respectively. Optimized aerogels dried under a supercritical condition not only showed the similar properties as conventional pure silica aerogels such as high transparency and porosity etc, but also demonstrated outstanding mechanical strength against compression; the aerogel drastically shrank upon loading and then recovered when unloaded, which is called a “spring-back” behavior. On ambient pressure drying, the wet gel also exhibited the similar response against compression stress originated from the capillary pressure, and thus xerogels with the comparative structure and properties to those of corresponding aerogels have also been obtained. This unusual mechanical behavior is attributed to the trifunctional flexible networks of MSQ, low silanol concentration which prevents the irreversible shrinkage, and high concentration of a hydrophobic methyl group directly attached to every silicon atom which helps re-expansion after the temporal shrinkage.     

Biodegradable and biocompatible inorganic–organic hybrid materials. I. Synthesis and characterization

The hydroxyl or vinyl end-groups of linear or three-arm star-shaped poly(ε-caprolactone) (PCL) chains have been derivatized into triethoxysilane groups reactive in the sol-gel process. New transparent hybrid materials that combine tetraethylorthosilicate (TEOS) and PCL known for biodegradability and biocompatibility have accordingly been prepared. The sol-gel process is, however, limited by the early vitrification of the reactive system. However, thermal posttreatment can overcome these diffusional and/or kinetic limitations as assessed by a set of analytical methods. The thermal stability of PCL is improved by incorporation into the silica network. Conversely, the thermal stability of the ceramer depends on the effective PCL content. The extent of PCL incorporation into the silica network depends on PCL molecular weight, number, and reactivity of the PCL functional groups. IR spectroscopy has shown that hydrogen bonding occurs between the ester groups of PCL and residual OH groups of the silicate component. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2295–2309, 1997     

New organic–inorganic hybrid structure based on paradodecatungstate clusters and imidazolium cations

An organic–inorganic hybrid material based on paradodecatungstate anions and imidazolium cations, Na₂(HIm)₈(H₂W₁₂O₄₂)·10H₂O (HIm: imidazolium), has been synthesized under mildly acidic conditions. This compound was characterized by single-crystal X-ray diffraction, IR and UV–visible spectroscopies, and thermogravimetric and differential thermal analyses. The compound crystallizes in the triclinic P-1 space group with a = 11.6945(8) Å, b = 12.4782(6) Å, c = 14.0952(9) Å, α = 106.041(3)°, β = 109.338(2)°, γ = 100.249(3)°, V = 1781.0(3) Å³, and Z = 2. The crystal structure exhibits an infinite 1D inorganic structure built from [H₂W₁₂O₄₂]^10? clusters and sodium cations; adjacent chains are further joined up by hydrogen-bonding interactions between protonated imidazole cations, water molecules, and polyoxoanions, to form a 3D supramolecular architecture.     

Biodegradable and bioactive hybrid organic–inorganic PEG-siloxane fibers. Preparation and characterization

A mixture of triethoxysilanefunctionalized poly(ethylene glycol), f-PEG, and tetraethoxysilane, TEOS, was used as precursors in the preparation of continuous hybrid f-PEG-siloxane sol–gel derived fibers. The fibers were spun by extrusion through a spinneret. The thus prepared fibers had a diameter of 20–50 m. ²⁹Si-CPMAS NMR measurements confirmed that the functionalized PEG is incorporated into the siloxane network through covalent bonds. The hybrid fiber elasticity was much higher than that of fibers spun from sols with TEOS as the only source for silica. However, the f-PEG chain length plays a crucial role for the spinnability of the sol, since, as a result of bridging flocculation, macroscopic phase separation occurred readily with increasing chain length of the f-PEG. The fibers were shown to be effective substrates for the nucleation and growth of bone-like hydroxyapatite.     

High-k titanium–aluminum oxide dielectric films prepared by inorganic–organic hybrid solution

In this paper, high-k titanium–aluminum oxide (ATO) dielectric film has been realized by using organic–inorganic hybrid precursor solution. X-ray diffraction pattern revealed that the ATO films (Ti content less than 67 at%) remain amorphous phase for annealing treatment at 400 °C. And all of the amorphous ATO films had very smooth and uniform surface with root mean square (RMS) roughness of less than 0.5 nm. Meanwhile, the results showed that the ATO film (Ti:Al = 1:8) had the best performance, including RMS roughness of 0.33 nm, relative permittivity of 15, and leakage current density of 1.41 × 10^?6 A/cm² at 1 MV/cm.     

Syntheses,structures and properties of four organic–inorganic hybrid nicotinate-bridging rare-earth-containing phosphotungstates

Four novel organic–inorganic hybrid nicotinate-bridging dimeric rare-earth (RE)-containing phosphotungstates [H₂N(CH₃)₂]₈[RE(H₂O)(NA)(α-HPW₁₁O₃₉)]₂·24H₂O (RE = Ho^III for 1, Er^III for 2, Tb^III for 3, Dy^III for 4; HNA = nicotinic acid) have been synthesized from the reaction of trivacant Keggin precursor Na₉[α-PW₉O₃₄]∙16H₂O, RE(NO₃)₃·6H₂O, HNA by employing dimethylamine hydrochloride as organic solubilizing agent in the conventional aqueous solution system, which have been further characterized by elemental analyses, IR spectra, thermogravimetric analyses and single-crystal X-ray diffraction. Structural analysis indicates that the hybrid dimeric {[RE(H₂O)(NA)(α-HPW₁₁O₃₉)]₂}⁸⁻ polyoxoanion in 1–4 can be considered as two head-to-head mono-RE-containing Keggin [RE(H₂O)(NA)(α-HPW₁₁O₃₉)]⁴⁻ subunits bridged by two (η²,μ-1,1)-nicotinate linkers, which stands for the first organic–inorganic hybrid RE-containing phosphotungstates functionalized by nicotinate ligands. What's more, the solid-state photoluminescence properties and lifetime decay behaviors of 1–4 have been measured at room temperature and their photoluminescence spectra display the characteristic emission bands of corresponding trivalent RE cations.     

Thermal and optical properties of novel polyurea/silica organic–inorganic hybrid materials

Current optical polymeric materials for advanced fiber laser development are susceptible to degradation due to the heat generated in high power usage. A suitable replacement light stripping material was explored to overcome this problem by examining optical and physical properties such as transmission/absorption, refractive index, thermal conductivity, and thermal stability. The synthesis and characterization of two new polyurea/silica ORMOSILs (ORganically MOdified SILicates) suitable for high temperature (up to 300 °C) optical applications are reported herein. A one-pot, room temperature synthesis is based upon commercially available bis-isocyanates and an amino-silane. These materials exhibit the combined traits of both glass and polymer by displaying optical clarity over a wide range of wavelengths stretching from the edge of the UV (250 nm) to well into the NIR (2,000 nm), refractive indices in the visible spectrum (n = 1.50–1.63), thermal conductivities of 0.26 ± 0.09 W/mK (ORMOSIL-A) and 0.27 ± 0.07 W/mK (ORMOSIL-B), and thermal stabilities up to 300 °C. The hybrid materials were found to be easily processed into films but thick casts (>2 mm) were subject to increased rates of cracking and longer curing times. Although this is typical of sol–gel chemistries, the organic constituents of ORMOSILs reduce this effect as compared to purely inorganic sol–gels. The effect of thermal aging on the materials’ properties will also be presented as well as a comparison of these materials and the current state of the art light stripping material.     

Enhancement of fluorescence and lasing properties of covalent bridged fluorescent dye in organic–inorganic hybrid materials

Fluorescent dye (DCM-OH) is covalently bridged to organic–inorganic hybrid material to prevent molecular stacking and to get high fluorescence efficiency and laser property. Novel DCM-OH is synthesized to have hydroxyl functional groups and is bridged to trialkoxysilane as a sol–gel precursor. It participates in sol–gel process to synthesize dye-bridged organic–inorganic hybrid material (dye-bridged hybrimer) and solid-state dye laser sample is ready through polymerization. Fluorescence property of dye-bridged hybrimer is compared with DCM-doped hybrimer that is simple mixture of DCM-OH and hybrimer matrix. The covalently bridged structure of hybrimer with DCM-OH prevented the stacking of fluorescent molecules and enhanced concentration stability. The dye-bridged hybrimer shows much higher fluorescence intensity and low color-shift until it reached high concentration in comparison with DCM-doped system. And the proper lasing property is observed in dye-bridged hybrimer samples.     

Synthesis and luminescence behavior of inorganic–organic hybrid materials covalently bound with pyran-containing dyes

A DCM derivative, namely 4-Dicyanomethylene-2-methyl-6-{[4′-(N-hydroxyethyl-N-methyl)amino]styryl}-4H-pyran (DCMH), has been synthesized and covalently incorporated into the inorganic silica network as pendants via a sol–gel process. Molecular structures of the resultants are confirmed by elemental analysis, ¹H NMR, DSC, TGA, FTIR and UV–Vis spectroscopy. Photoluminescence (PL) spectra shows that the emission of DCMH peaked at 625 nm is almost completely quenched in DMF solution with a concentration of 1 × 10⁻⁴ mol/L, however, in hybrid films, the PL intensity enhances obviously with increasing DCMH concentration even at the high loading content of 40 mol%. All the hybrid films exhibit PL emission around 646–650 nm and the peak position reveal little dependence on the concentration of dye, suggesting they can be used as red emissive materials in light-emitting diodes. The relationship between fluorescence lifetime and dye concentration is also investigated by time-resolved PL measurements.     

Responsive microstructures on organic–inorganic hybrid films

Micro-periodic structures exhibiting shape memory have been fabricated on organic–inorganic hybrid films. The microscale structures are obtained by forming wrinkles via buckling of the stiff surface layer. The surface-modified layers are obtained by surface photopolymerization or by oxidation of the hybrid films. The microscale structures are spontaneously formed by the shrinkage of the underlayer via gelation. The surface microstructures on titania- or silica-based films with hydrophilic swellable polymers exhibit a humidity response, i.e., a shape memory effect. This is observed when the surface microstructure disappears and is subsequently recovered with cyclic variation of the surrounding humidity. Micro-rolls are also fabricated by the selective swelling of surface-modified layers.     

Sedimentation analysis of organic–inorganic hybrid colloids

Hybrid organic–inorganic latex particles are synthesized to combine the beneficial properties of the constituents which thus lead to synergistic improvement in the properties. The properties of hybrid particles are dependent on the successful hybridization process, thus controlling or tuning of such processes by effective characterization is immensely important. Analytical ultracentrifugation provides these characterization possibilities owing to its high statistical capability and ability to characterize multiple parameters. The use of different detection methodologies can help in generating valuable information on the overall size and density distributions of the particles. Apart from that, it is also possible to quantify the presence of any free polymer and inorganic particles in the hybrid latex which would affect the properties of hybrid latexes. By following the densities of the pure and hybrid particles, it is also possible to quantify the amounts of the constituent phases in the hybrid particles. The density gradients generated in preparative ultracentrifugation also provide additional possibilities for the characterization of the hybrid particles which have densities higher than the measurable range in the analytical ultracentrifuge. Evolution of hybrid particles can also be studied as a function of time. It also provides advantage of separation of the various fractions for further characterization.     

A new organic–inorganic hybrid based on Mn–salen and decavanadate

An organic–inorganic hybrid based on Mn-salen and decavanadate, [NH₄]₂[Mn(salen)(H₂O)₂]₄[V₁₀O₂₈]?·?6H₂O (1) (salen?=?N,N′-ethylene-bis(salicylideneiminate)), has been synthesized by the strategy of secondary building units in mixed methanol–water solution and was structurally characterized by single-crystal X-ray diffraction, elemental analyses, IR, and UV-Vis. The [Mn(salen)(H₂O)₂]⁺ cations and water molecules are located in the interspaces among the polyoxoanions [V₁₀O₂₈]^6? forming a POM-based supramolecule. Compound 1 is the first example of metal-Schiff-base polyoxovanadates. The photocatalytic analysis, cyclic voltammetry, and electrocatalytic analysis of 1 have been investigated.     

Synthesis and structure of a new polyoxometalate-based inorganic–organic hybrid and application as a chemically bulk-modified electrode

A new Keggin-type polyoxometalate-based inorganic–organic hybrid, [Cu(H₂O)₂(daphen)]₂[SiW₁₂O₄₀]·9H₂O (1) (daphen?=?5,6-diamino-1,10-phenanthroline), was hydrothermally synthesized, and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, fluorescence spectra, and thermal analysis. Single-crystal X-ray diffraction analysis reveals that in 1, [SiW₁₂O₄₀]^4? is a tetradentate ligand with its four terminal oxygens coordinating to four Cu(II)–daphen fragments to form a 2D sheet with (4,4) topology. On the basis of the insolubility of 1 in water and common organic solvent and its reversible multielectron redox processes, 1 was used to fabricate a bulk-modified carbon paste electrode (1-CPE) by direct mixing. Electrochemistry indicated that 1-CPE is stable over hundreds of cycles and possessed electrocatalytic activity toward the reduction reactions of nitrite.     

Well-defined difunctional POSS macromers and related organic–inorganic polymers: Precision synthesis,structure and properties

Polyhedral oligomeric silsesquioxanes (POSS) are a class of well-defined organic–inorganic stereo molecules comprising inorganic Si O Si cores and peripheral organic moieties. Since they were first reported in 1946 by Scott et al., there have been a great number of investigations on the use of POSS macromers as the building blocks to access the organic–inorganic composites with polymers. In most of cases, monofunctional POSS macromers are employed and the linear hybrid polymers are obtained. Under this circumstance, POSS cages act as the side or end groups whereas the main chains of the polymers remain unchanged. Occasionally, octafunctional POSS macromers are involved, resulting in the generation of crosslinked (or network-like) hybrids. Recently, well-defined difunctional POSS macromers have increasingly provoked a considerable attention of investigators. From the synthetic methodology of POSS macromers to the approaches to introduce them into polymers, difunctional POSS macromers have the features quite different from mono- (or octa-) functional POSS. More importantly, the related organic–inorganic hybrids possess the different morphologies and properties. In the past years, there has been a rapid increase in the number of literatures on the studies on well-defined difunctional POSS and the related organic–inorganic hybrids. Nonetheless, the related review is lacking. In this contribution, we would summarize the recent progress in this regard, from the synthesis of POSS macromers, the approaches of introducing the POSS macromers into polymers to the correlation of morphologies with properties of the organic–inorganic hybrids. In addition, perspectives and challenges for the further advancement are envisaged and discussed.     

Four inorganic–organic hybrid complexes built from tetravanadate and macrocyclic oxamide

Four inorganic–organic hybrid compounds, [M₂(CuL)₄(V₄O₁₂)]·2H₂O (M?=?Co (1), Mn (2)), [Mn₂(NiL)₄(V₄O₁₂)]·2H₂O (3), and [Zn₂(CuL)₄(V₄O₁₂)]·2CH₃OH·2H₂O (4) (M′L, H₂L?=?2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien), have been synthesized and characterized by elemental analysis, IR, UV, fluorescence spectra, and X-ray diffraction analysis. Single-crystal X-ray analysis reveal that both [V₄O₁₂]^4? and M₂V₄ adapt a chair-like configuration in four structures. The cyclovanadate group [V₄O₁₂]^4? is a tetradentate bridging ligand linking two [M(M′L)₂]²⁺ fragments, producing centroantisymmetric heterometallic hexanuclear [M₂M′₄] complexes. The variable-temperature magnetic susceptibility measurements (2–300?K) of 1 and 2 show weak antiferromagnetic interactions.     

Effect of modified organic–inorganic hybrid materials on thermal properties of cotton fabrics

Phosphorus-modified siloxanes monomer DOPO-IPDI-AMEO (DIA) was synthesized and characterized by ¹H nuclear magnetic resonance (H NMR), ³¹P NMR, and Fourier transform infrared spectra (FTIR). It hydrolyzed and grew an organic–inorganic hybrid coating on the surface of cotton fabrics via sol–gel process. The conversion of gel reaction was characterized by solid-state ²⁹Si NMR. The effect of the modified organic–inorganic hybrid materials on thermal properties of cotton fabrics was investigated by thermogravimetric (TG) analysis, real time Fourier transform infrared (RT-FTIR), and microscale combustion calorimetry (MCC) experiments. In addition, thermogravimetry-Fourier transform infrared spectra (TG-FTIR) were used to investigate the released degradation products. The characterization information represented that DIA has been prepared successfully. Also the conversion of gel reaction was fairly high. The TG data showed that char residues increased with the addition of the DIA coating. While the peak heat release rate (PHRR) decreased with the presence of the coating in MCC test. Moreover, the flammable degradation products dropped obviously, which can be observed from the data of TG-FTIR.     

Investigation of inorganic–organic hybrid materials containing polyoxometalate cluster anions and organic dye cations

Two new ionic-pair salts containing an organic dye cation, i.e. New Fuchsin or Pararosaniline cation, with Keggin-type POMs, [SiW₁₂O₄₀]^4? and [BW₁₂O₄₀]^6?, have been isolated under hydrothermal conditions. [(C₂₂H₂₄N₃)₄][SiW₁₂O₄₀] (1) and [(C₁₉H₁₈N₃)₆][BW₁₂O₄₀] (2) have been characterized by elemental analyses, FT-IR and single crystal X-ray crystallography. Both of these complexes have strong absorption in the visible-light range due to the involvement of the organic dye and both show weak fluorescence emission.     

Multi-component hybrid inorganic–organic–inorganic particles with various metal oxide outer shells

Non-agglomerated hybrid particles of 200 nm diameter with an outer metal oxide shell were prepared by reacting the COOH groups of poly((S)-N-dicarbazolyl-lysine)-covered silica particles with metal alkoxides, such as titanium, zirconium and aluminum alkoxides, followed by sol–gel processing. With tetraethoxysilane (Si(OEt)₄), the silica particle core was growing rather than forming an external metal oxide shell, as observed for the other tested metal alkoxides.