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.     

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.     

Solid polymer electrolytes X: Preparation and characterizations of polyether–siloxane,organic–inorganic,hybrid nanocomposites complexed with lithium perchlorate

Organic–inorganic hybrid nanocomposites of poly(ethylene glycol)/siloxane were obtained via the sol–gel approach. In these composites, nanometric siloxane heterogeneity was embedded into a polymer matrix with a covalent bond at the interfaces. The ²⁹Si magic-angle spinning (MAS) spectrum exhibited a high degree of condensation through the relative abundance of T⁰ [RSi(OR)₃], T¹ [RSi(OR)₂(OSi)], T² [RSi(OR)(OSi)₂], and T³ [RSi(OSi)₃] silicone nuclei. The effect of lithium salt concentration on ionic interaction, conductivity, and thermal properties of these composite electrolytes were investigated by Fourier transform infrared spectroscopy, DSC, thermogravimetric analysis, alternating current impedance, and solid-state ⁷Li MAS NMR measurements. These observations indicated that the different types of complexes by the interactions of Li⁺ and ClO ions are formed within a hybrid host, and the formation of transient crosslinks between Li⁺ ions and the ether oxygens results in an increased glass-transition temperature of the polyether segment and decomposed rate of composite electrolyte. ⁷Li MAS NMR measurements revealed the changes in line shape of lithium resonances with different LiClO₄ contents, suggesting that a significant degree of ionic association is present in the polymer-salt complexes. The behavior of ion transport in these composite electrolytes was correlated with the interactions between ions and polymer host. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1928–1937, 2004     

Synthesis,characterization and luminescence properties of a coordination polymer based on self-assembly of PrIII with inorganic–organic hybrid bridging ligands

A new coordination polymer having the formula [Pr(μ ₅-S₂O₃)(μ ₄-tp)_0.5(H₂O)] _n (1) (S₂O₃ = thiosulfate dianion; tp = terephthalate dianions) was obtained by in situ reaction of Pr₂(SO₄)₃ · 6H₂O with H₂tp ligands under solvothermal conditions (H₂O/ethanol). The coordination polymer obtained was characterized by elemental analysis, FT-IR, thermogravimetry (TG), fluorescent spectra and single crystal X-ray diffraction analysis. The most intriguing structural feature is that the complex exhibits a 3D open framework resulting from bridge-linking coordination between ligands and praseodymium ions. Additionally, 1 has characteristic emission spectra of Pr^III with good fluorescence properties. This is the first coordination polymer based on thiosulfate/terephthalate ligands and a rare earth metal and has an unprecedented pentadentate-bridge-linking coordination mode of the thiosulfate group.     

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.     

Synthesis and characterization of new hybrid inorganic–organic polymer nanocomposite as efficient catalyst for oxidative desulfurization of real fuel

Sulfur-containing compounds are responsible for much air pollution, and therefore eliminating these compounds is of importance. Herein, a hybrid organic–inorganic recyclable nanocatalyst (TBA-PW₁₁Ni@PANI) was synthesized successfully to investigate its effects on the catalytic oxidative desulfurization (CODS) process of real gasoline/model fuel. To this end, the Keggin-based mono-lacunary polyoxometalate [PW₁₁NiO₃₉] was prepared and modified with quaternary cation tetrabutylammonium (TBA). Then, this was further immobilized on polyaniline (PANI) via the sol–gel method. The synthesized nanocomposite was characterized using various techniques. The high dispersion of polyoxometalate on PANI was confirmed. Also, it was found that the crystalline structure remained unaltered after immobilization. In addition, the effects of various parameters such as dosage and temperature on the CODS of model fuel in the presence of H₂O₂–acetic acid (1:2 v/v) were studied in detail. Moreover, the kinetics of the CODS process was also studied and a mechanism proposed. According to the results, TBA-PW₁₁Ni@PANI showed an efficiency of up to 97% with 0.1 g at 35°C (optimum values) which implies its good catalytic functionality in the CODS process. Finally, the TBA-PW₁₁Ni@PANI catalyst displayed long-term stability and good reusability after five runs.     

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.     

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.     

Assessment of adsorption properties of inorganic–organic hybrid cyclomatrix type polyphosphazene microspheres for the removal of Pb(II) ions from aqueous solutions

Abstract

Inorganic–organic hybrid cyclomatrix type polyphosphazene microspheres (poly[cyclotriphosphazene-co-(4,4′-diaminodiphenylmethane)]) (HDMS) and poly[cyclotetraphosphazene-co-4,4′-diaminodiphenylmethane)] (ODMS) were prepared to investigate their possible use as alternative adsorbents for the comparative study on Pb(II) ions removal from aqueous solutions. The structures of the microspheres were elucidated by Fourier Transform Infrared (FTIR) spectroscopy and Dynamic Light Scattering (DLS) measurements, and the surface morphologies were also observed by Scanning Electron Microscopy (SEM). The adsorption of Pb(II) ions onto HDMS and ODMS from aqueous solutions was examined by means of pH, temperature, contact time and concentration. Furthermore, adsorption kinetics and isotherm models were applied and the experimental data fitted well with Langmuir isotherm and pseudo-second-order kinetic models. The maximum adsorption capacities of HDMS and ODMS for Pb(II) ions were obtained as 157.8 and 308.0?mg g^?1 at 20?°C and pH 5.5, respectively.     

Synthesis,structures and electrochemical properties of four organic–inorganic hybrid polyoxometalates constructed from polyoxotungstate clusters and transition metal complexes

Four novel organic–inorganic hybrid compounds [Cu₅ ^I(4,4′-bpy)₃(2,2′-bpy)₄][BW₁₂O₄₀] · H₂O (1), [Ni_0.5(2,2′-bpy)_1.25][Ni(2,2′-bpy)₃][Ni(2,2′-bpy)₂(H₂O)(SiW₁₁^VIW^VO₄₀)] · 0.5H₂O (2), [H₂bpy]₂[Zn(2,2′-bpy)₃]₂[Si₂W₁₈O₆₂] · 1.5H₂O (3) and [Cu^II(2,2′-bpy)₂]₂[SiW₁₂O₄₀] · 2H₂O (4) (2,2′-bpy = 2,2′-bipyridine, 4,4′-bpy = 4,4′-bipyridine) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis, electrochemical measurements and single-crystal X-ray diffraction. Compound (1) is a novel [BW₁₂O₄₀]⁵⁻ polyoxoanion bisupported by copper(I) coordination cations with mixed 2,2′-bpy and 4,4′-bpy ligands. Compound (2) is constructed from the [SiW₁₁^VIW^VO₄₀]⁵⁻ polyoxoanions supported by [Ni(2,2′–bpy)₂]²⁺. Compound (3) is composed of a novel [Si₂W₁₈O₆₂]⁸⁻ cluster and [Zn(2,2′–bpy)₃]²⁺ complexes, which held together into a three-dimensional (3D) supramolecular network through hydrogen-bonding interactions. Compound (4) shows a 2D layer framework constructed from a bisupporting Keggin polyoxoanion cluster and [Cu(2,2′–bpy)₂]²⁺ coordination polymer fragments, resulting in 3D networks via supramolecular interactions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dye-sensitized solar cell with a solid state organic–inorganic composite electrolyte containing catalytic functional polypyrrole nanoparticles

An organic–inorganic composite electrolyte with tetra-n-butyl titanate and ethylene glycol is prepared with sol–gel method and used in fabricating solid state dye-sensitized solar cell (S-DSSC). The addition of acetyl acetone into the composite electrolyte can extend the solidification time to meet the time requirement for assembling S-DSSC. The addition of 4-tert-butylpyridine can enhance the photovoltaic performance of S-DSSC due to its efficient suppressing of dark current in S-DSSC. Furthermore, with the addition of catalytic functional polypyrrole nanoparticles for transformation of iodide/triiodide redox couples in the composite electrolyte, the energy conversion efficiency of S-DSSC increases from 3.147 to 3.597%, with 14% enhancement.     

Synthesis,characterisation and ion exchange properties of hybrid organic–inorganic composite material: polyacrylamide zirconium (IV) iodosulphosalicylate

ABSTRACT

Contamination of groundwater by heavy metal is one of the most emerging and serious environmental problems. There are so many methods which are available to overcome these problems. Among various available methods, hybrid organic–inorganic ion exchange resin has become more popular due to certain advantages over other available conventional methods; hence, in the present proposed work, we synthesised a hybrid organic–inorganic composite material polyacrylamide zirconium (IV) iodosulphosalicylate by using the sol-gel technique. Synthesised resin was characterised by various methods like Infrared spectroscopy and Thermogravimetric analysis-Differential thermal analysis. Various samples of this ion exchange resin are prepared by changing the condition of synthesis, i.e. concentration of acrylamide to rationalise the ion exchange capacity of the synthesise hybrid organic–inorganic ion exchange resins. A mixture of 0.1 M potassium iodate, 0.1 M sulphosalicylic acid and 0.1 M acrylamide was added dropwise to 0.4 M zirconium oxychloride accompanied by constant stirring for 8 h using magnetic stirrer at 70°C to yield polyacrylamide zirconium (IV) iodosulphosalicylate with maximum ion exchange capacity. Ion exchange capacity of synthesised resin was determined by column method and the maximum ion exchange capacity was found for Pb(II). Determination of k_d values shows that the resin was highly selective for Pb (II).The selectivity for Pb was also evaluated by using certain binary mixture separation such as Ni (II)-Pb(II), Cu(II)-Pb(II), Cd(II)-Pb(II), Sr(II)-Pb(II), Ba(II)-Pb(II),Zn(II)-Pb(II) and Mg(II)-Pb(II).     

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.     

Role of surface modification of colloidal CdSe quantum dots on the properties of hybrid organic–inorganic nanocomposites

In this work, tri-octyl phosphine/tri-octyl phosphine oxide (TOPO)-capped cadmium selenide (CdSe) quantum dots (QDs) of varied sizes (5–9 nm), prepared by varying the input Cd:Se precursor ratio using chemical route, were dispersed in conducting polymer matrices viz. poly[2-methoxy, 5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly(3-hexylthiophene) (P3HT). By using a binary solvent mixture (pyridine–chloroform), homogeneous dispersion of CdSe nanocrystals in polymers (MEH-PPV, P3HT) could be realized. The properties of the resulting dispersions could be tailored by the composition and concentration of QDs in polymer. The emission and structural properties of polymer–CdSe nanocomposites are found to be dependent on the crystallite size and morphology of CdSe nanocrystallites. An effective quenching of photoluminescence emission in the polymer nanocomposite was observed for smaller CdSe quantum dots (size ∼6 nm) as compared to larger CdSe quantum dots (size ∼9 nm), thus ensuring efficient charge transfer process across the polymer–CdSe interface in the former case. The incomplete quenching, particularly for MEH-PPV:CdSe nanocomposites, could be as a result of insufficient coverage of polymers on the surface of CdSe nanocrystallites, mainly due to phase segregation for TOPO-stripped CdSe nanocrystallites. The superior morphology and optical properties of polymer nanocomposite (P3HT:CdSe QDs) could play a pivotal role for the realization of effective charge separation and transport in hybrid solar cells.     

Improvement of the bioactivity of organic–inorganic hybrid aerogels/wollastonite composites with TiO2

Organic–inorganic hybrid aerogels containing P and Ti have been synthesized by supercritical drying of alkogels prepared by hydrolysis and poly-condensation of metalo-organic precursors under high-power ultrasound. These materials become bioactive when doped with Ca. Wollastonite particles (CaSiO₃) were added as an active phase, instead of incorporating Ca into the aerogel atomic network. These particles had previously been precipitated and were then added to the sol. The aerogels were studied by Fourier transform infrared analysis, scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction and N₂ adsorption. The stress–strain behaviours were evaluated under compression to obtain the Young’s modulus. It was found that the incorporation of TiO₂ into wollastonite-P₂O₅ hybrid aerogels increased their capacity to form apatite and, consequently, improving their bioactive response.     

Photo‐optical properties of polymer composites based on stretched porous polyethylene filled with photoactive cholesteric liquid crystal

A new type of polymer–liquid crystal composite with photovariable dichroism and birefringence is described. Porous stretched polyethylene films were used as polymer matrices. To induce a cholesteric phase in a commercial nematic host, a chiral photochromic dopant based on sorbide and cinnamic acid capable of E–Z isomerization under UV irradiation was used. A merocianine‐type substance was selected as a dichroic dye. Introduction of a dye‐doped cholesteric mixture with a helical pitch higher than ～300 nm to polymer film led to an almost complete transition from a cholesteric to an oriented nematic phase, as well as to an increase in birefringence and the appearance of dichroism. Decrease of the helical pitch by increasing in the chiral dopant concentration in the liquid crystal–polymer composite results in a reduction of the dichroism values. UV irradiation of polymer composite leading to an isomerization of the chiral dopant and helix untwisting induces a noticeable gradual growth of dichroism and birefringence. These new composites can be considered as promising materials for optical applications.     

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.     

Three inorganic–organic hybrid compounds based on Keggin polyoxometalate and transition metal complexes: crystal structures and electrochemical properties

Polyoxometalate (POM)-based coordination polymers, [Cu(L)₂][SiW₁₂O₄₀]·4py·H₂O (1), [Ag(py)₂]₄[SiW₁₂O₄₀] (2) and [Co(L)₃]₂[SiW₁₂O₄₀]·py·7H₂O (3) (L?=?pyridine-2-carboxylic acid, py?=?pyridine), have been obtained hydrothermally and characterized by elemental analyses, IR and single-crystal X-ray diffraction analyses. Electrochemical properties are also investigated.     

Fabrication of core/shell hybrid organic–inorganic polymer microspheres via Pickering emulsion polymerization using laponite nanoparticles

Oil-in-water (o/w) emulsions of styrene, as monomer oil in water, were achieved successfully via Pickering emulsification with laponite nanoparticles as the sole inorganic stabilizers. The formed emulsions showed excellent stability not only against droplets coalescence (before polymerization) but also against microparticles coagulation (after polymerization). Generally, the number of composite polystyrene microparticles (PS) increased and their sizes decreased with the content of solid nanoparticles used in stabilizing the precursor o/w emulsions. This is consistent with the formation of rigid layer(s) of the inorganic nanoparticles around the PS microparticles thus a better stability was achieved. The composite microparticles were characterized using various techniques such as surface charge, stability, transmission electron microscope (TEM), scanning electron microscope (SEM) and Fourier transform infra-red (FT-IR). Coating films of the prepared latexes were applied to flat glass surfaces and showed reasonable adhesion compared to PS latex particles prepared with conventional surfactants. The effect of employed conditions on the features of the resulting emulsions in terms of stability and particle size has been discussed.     

pH-Controlled assembly of two POM-based inorganic–organic hybrid copper coordination polymers: synthesis,structures and properties

Transition Metal Chemistry - Two POM-based copper coordination polymers constituted by Keggin-type polyoxometalates (POMs), [Cu2 (SiW12O40)2 (Fbtx)3 (H2O)4]n (1) and {[Cu2 (SiW12O40) (Fbtx)2...