Hybrid Matrices Research Articles

Reconfigurable K-Band MIMO Transmission With On-Board Vector Calibration

This paper presents a reconfigurable multi-input and multi-output amplifier architecture with on-board multiport vector calibration (MVC) for flexible multi-channel transmission in K-band. The proposed architecture controls phases of K-band transmission path to generate a diversity of source-to-target channel power assignment. In addition, the proposed calibration circuitry detects relative amplitude and phase of each transmission path and ensures high isolation at each output port. The proposed architecture consists of waveguide hybrid matrices, amplifier modules, including phase shifter, attenuator and 0°/180° phase inverter monolithic microwave integrated circuits (MMICs), and a MVC block. The MVC is configured with a modulator, two QPSK demodulator MMICs, a digital signal processing board, and 16 digital-to-analog converter units. For the verification of K-band applications, $4\times4$ multi-channel front end was implemented and showed reconfigurable performance as well as stable port-to-port isolation characteristics better than 26 dB from 19.5 to 22.5 GHz.

Interfacial adhesion improvement in carbon fiber/carbon nanotube reinforced hybrid composites by the application of a reactive hybrid resin initiated by gamma irradiation

Interfacial adhesion is a key factor in composite materials. The effective co-working of the reinforcing materials and matrix is essential for the proper load transfer between them, and to achieve the desired reinforcing effect. In case of nanocomposites, especially carbon nanotube (CNT) reinforced nanocomposites the adhesion between the CNTs and the polymer matrix is poor. To improve the interfacial adhesion and exploit the reinforcing effect of these nanoparticles a two step curable epoxy (EP)/vinylester (VE) hybrid resin system was developed where the EP is cured using hardener in the first step, during the composite production, and in the second step the curing of the VE is initiated by gamma irradiation, which also activates the reinforcing materials and the cured matrix component.A total of six carbon fiber reinforced composite systems were compared with neat epoxy and EP/VE hybrid matrices with and without chemical initiator and MWCNT nano-reinforcement. The effect of gamma irradiation was investigated at four absorbed dose levels. According to our three point bending and interlaminar shear test results the adhesion has improved between all constituents of the composite system. It was demonstrated that gamma irradiation has beneficial effect on the static mechanical, especially interlaminar properties of both micro- and nanocomposites in terms of modulus, strength and interlaminar shear strength.

Carboxymethyl fenugreek galactomannan-gellan gum-calcium silicate composite beads for glimepiride delivery

Novel carboxymethyl fenugreek galactomannan (CFG)-gellan gum (GG)-calcium silicate (CS) composite beads were developed for controlled glimepiride (GLI) delivery. CFG having degree of carboxymethylation of 0.71 was synthesized and characterized by FTIR, DSC and XRD analyses. Subsequently, GLI-loaded hybrids were accomplished by ionotropic gelation technique employing Ca+2/Zn+2/Al+3 ions as cross-linkers. All the formulations demonstrated excellent drug encapsulation efficiency (DEE, 48–97%) and sustained drug release behaviour (Q8h, 62–94%). These quality attributes were remarkably influenced by polymer-blend (GG:CFG) ratios, cross-linker types and CS inclusion. The drug release profile of the optimized formulation (F-6) was best fitted in zero-order model with anomalous diffusion driven mechanism. It also conferred excellent ex vivo mucoadhesive property and considerable hypoglycemic effect in streptozotocin-induced diabetic rats. Furthermore, the beads were characterized for drug-excipients compatibility, drug crystallinity, thermal behaviour and surface morphology. Thus, the developed hybrid matrices are appropriate for controlled delivery of GLI for Type 2 diabetes management.

Superhydrophobic Coatings on Aluminium Based on Carboxylic Acids

Development of new coatings for corrosion protection should be directed to environmentally friendly yet efficient technologies. Industrial applications additionally demand energy sustainability and cost effectiveness. Among varieties of new coatings being developed superhydrophobic coatings are also in the focus of current research in both academic and industrial sectors. The background of their use, inspired by effects in nature, is the prevention of ingress of electrolyte to underlying substrate and properties of self-cleaning and anti-sticking. Superhydrophic surfaces can be applied to different substrates, from metal, textile, plastics, etc. Superhydrophobicity can be related to surface texture or surface chemistry, e.g., use of silane-, fluoro-based or other compounds [1]. The basic idea of the current research study is to design multifunctional compounds by integrating corrosion inhibitors and hydrophobic agents with lipophilic or fluorous properties into hybrid matrices so as to produce a corrosion resistant hydrophobic coating that display good adhesion to Al substrates. The first step is to test potential candidates for (i) hydrophobic compounds and (ii) corrosion inhibitor compounds. Among hydrophobic compounds, carboxylic acids were tested since they offer environmentally friendly and cheap option. In order to adsorb carboxylic acids on metal surface an appropriate pre-treatment is required. In the present work we investigated the possibility to fabricate superhydrophobic surfaces on aluminium metal pre-treated by alkaline etching at 90 °C [2] which represents a green solution-phase method to produces hierarchical growth of the aluminium hydroxide array. After immersion in ethanol solution of carboxylic acid the surface turns superhydrophobic. In the present study we have investigated the effect of several parameters on the formation of superhydrophobic surface on aluminium pre-treated by etching: type of etching as a pre-treatment, length of carboxylic chain, time of immersion in carboxylic acid and concentration of carboxylic acid. The effect of these parameters on the water contact angle and corrosion properties in 0.5 M NaCl solution were determined. Depending on the type of carboxylic acid a remarkable decrease in both cathodic and anodic current density can be achieved. Optimal parameters were denoted as those achieving high water contact angle, and low corrosion current density combined with a broad passive range. XPS showed that after alkaline etching the aluminium surface was fully covered by an hydroxide layer. ToF-SIMS provided direct evidence of adsorption of octanoic and stearic acids. Coatings prepared on Al by self-assembling in carboxylic acids were tested also by long-term immersion in NaCl solution. Surface durability in terms of resistance in acid and alkaline solution, as well as sliding angle were determined. Morphology of self-assembled carboxylic layers on alkaline etched aluminium analysed by FE-SEM shows nano-rough surface with numerous micro-cones with steps or terraces giving the surface a dual roughness. Composition of the surface was investigated using various surface analytical methods, i.e. FTIR, XPS and SIMS. Adsorption bonding of carboxylic acids to hydroxylated Al surfaces is also being investigated by DFT calculations. We utilized periodic slab model of passivated surface with hydroxylated oxide-layer supported on Al metal. These calculations help us to scrutinize details of how carboxylic head-groups attach to hydroxylated surface and how lateral intermolecular interactions and their self-assembly depends on the length of the aklyl tail. The effect of the organic layer composition on the resulting electronic properties of the passive layer (band gap, electronic workfunction) is also investigated. Fig. 1. FE-SEM image of aluminium surface etched in NaOH and immersed in 5 mM ethanol solution of stearic acid. Detail: contact angle of water drop 156°. Acknowledgments: This work is a part of M.ERA-NET project entitled “Design of corrosion resistant coatings targeted for versatile applications”, acronym COR_ID. The financial support of the project by Ministry of Education, Science and Sport of Republic of Slovenia (Programmes of International Scientific Cooperation) and Agence Nationale de la Recherche, France, is acknowledged.

Carbonization, Hydrogenation, Oxidation and Electromagnetic Absorption of TiOx‐Pyrrole Compounds

This work presents a morphologic, structural and electromagnetic absorption study in plasma‐synthesized organometallic hybrid compounds based on titanium oxide and pyrrole, which could potentially be used as photoconductive materials in solar cells. The synthesis was carried out with the combination in liquid phase of titanium tetra isopropoxide and pyrrole with 1:1 mass ratio in a glass vacuum tubular reactor with resistive electric discharges and reaction intervals from 60 to 240 min. Films and particles were formed with mean particle diameter of 438 nm. The hybrid compounds presented functional groups with multiple bonds related with pyrrole and TiOx structures. Organic and inorganic phases were detected in the hybrid matrices in which carbonization, hydrogenation, oxidation and nitridation were quantified which suggested strong dehydrogenation and the formation of multiple bonds in the plasma reactions. The compounds absorbed electromagnetic radiation in two regions with different intensity. The first and most intense one was between 190 and 350 nm wavelength, the second one was identified from 350 to 800 nm, this effect suggests that the titanium oxide is the dominant fraction in the first region and pyrrole in the second.

Kaolinite-polymer compounds by grafting of 2-hydroxyethyl methacrylate and 3-(trimethoxysilyl)propyl methacrylate

Novel kaolinite-polymer solids containing methacrylate groups were prepared by functionalization of the Brazilian São Simão kaolinite with the monomers 2-hydroxyethyl methacrylate (HEMA) and 3-(trimethoxysilyl)propyl methacrylate (TMSPM). Functionalization involved reflux of the monomers in the presence of kaolinite previously intercalated with dimethylsulfoxide (DMSO). HEMA and TMSPM effectively displaced DMSO molecules from the clay mineral interlayer, forming AlOC bonds in organic-inorganic hybrid matrices. The resulting materials were characterized by powder X-ray diffraction, thermal analysis, infrared spectroscopy and TEM analysis. Powder X-ray diffraction evidenced the intercalation of DMSO, and its substitution by HEMA and TMSPM. Thermal analyses indicated that HEMA- and TMSPM-functionalized kaolinite materials were thermally stable up to 300°C. The shift of the infrared bands due to interlayer hydroxyl groups and the presence of bands due to characteristic vibrations of the methacrylate groups (3349, 3331, 3290, and 1589cm−1) also confirmed the functionalization of the kaolinite with the monomers. The ability of both monomers to graft methacrylate groups onto kaolinite interlayer space was also analyzed. The solids obtained were used as adsorbents of dye methylene blue (MB), showing that the clay nanocomposites could remove the dye more efficiently than the isolated precursors (pure kaolinite and the polymers) separately. The kinetics of the process followed a pseudo-second order model and equilibrium fitted well to the Freundlich model.

Complex-Emulsion synthesis of organo-inorganic amphiphilic sorbents with specific affinity for glucose

Granular organo-inorganic amphiphilic sorbents with specific affinity for glucose were synthesized with the aim of developing selective hemosorbents for efferent therapy of hyperglycemia. The sorbents were prepared in oil/water/oil complex emulsions by copolymerization of 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate on the surface of selenium nanoparticles stabilized with polyvinylpyrrolidone. The phases were stabilized with excess selenium/polyvinylpyrrolidone nanocomplexes. Optimum synthesis conditions ensuring formation of hybrid sorbents with the physicochemical properties required for performing efficient preparative hemosorption and plasma adsorption processes were found. The specific affinity for glucose was reached by modification of these sorbents via imprinting with template glucose molecules in the surface polymer layer and via introduction of boric acid as an affine ligand into the hybrid matrices.

Analysis and synthesis of cascaded metasurfaces using wave matrices

Various matrix representations are used to analyze the propagation of electromagnetic waves through stratified (layered) media or cascaded circuit networks. These include ABCD matrices, scattering matrices, impedance matrices, and hybrid matrices. A less known network representation is the wave matrix. In this paper, a brief review of wave matrices is presented and their relation to other network representations derived. Wave matrices are found for common interfaces such as boundaries between dielectric media, dielectric slabs, as well as electric, magnetic, and magneto-electric sheet boundaries (generalized sheet transition conditions). These results are then used to develop an analytical synthesis approach for cascaded metasurfaces: metasurfaces consisting of a cascade of sheets separated by dielectric spacers. This is in contrast to earlier works which relied on numerical solvers or optimization methods to design such structures. A few design examples are presented to demonstrate the utility of the synthesis approach.

Comparison of Some Multivariable Hybrid Resultant Matrix Formulations

Objective: To evaluate and compare different hybrid resultant formulations in relation to computational complexity, performance and optimality condition. Methods/Statistical Analysis: Hybrid matrices are evaluated using computer algebra system. Findings: we have shown that, none of the hybrid formulation works well with the exception of HDP4. However, after deleting the zero rows and columns the resulting matrix may not be a square matrix, on the other hand, we studied and established that none of the hybrid formulation produces a square matrix in general and likewise predicted that, the density or sparseness of the polynomial equations does not influence the performance of these hybrid matrix formulations. Applications/Improvements: This comparison reveals that, the existing hybrid methods for computing resultant are not efficient and therefore there is need for another formulations with will focus on the current limitations described in this paper.

Flexible, cathodoluminescent and free standing mesoporous silica films with entrapped quasi-2D perovskites

The effective entrapment of hybrid organic-inorganic semiconductors (HOIS) into mesoporous polymer-silica hybrid matrices, formed as free standing flexible films, is presented for the first time. A blend of quasi-2D HOIS, simply synthesized by mixing two-dimensional (2D) and three dimensional (3D) HOIS, exhibiting strong photoluminescence, is embedded into porous silica matrices during the sol-gel synthesis, using tetraethylorthosilicate as precursor and Pluronic F-127 triblock copolymer as structure directing agent, under acidic conditions. The final nanostructure hybrid forms flexible, free standing films, presenting high cathodoluminescence and long stable excitonic luminescence, indicating the protective character of the hybrid matrix towards the entrapped perovskite. A significant result is that the photoluminescence of the entrapped HOIS is not affected even after films’ prolonged exposure to water.

Hybrid Aorta Constructs via In Situ Crosslinking of Poly(glycerol-sebacate) Elastomer Within a Decellularized Matrix.

Decellularization of tissues and organs has high potential to obtain unique conformation and composition as native tissue structure but may result in weakened tissue mechanical strength. In this study, poly(glycerol-sebacate) (PGS) elastomers were combined with decellularized aorta fragments to investigate the changes in mechanical properties. PGS prepolymer was synthesized via microwave irradiation and then in situ crosslinked within the decellularized aorta extracellular matrix (ECM). Tensile strength (σ) values were found comparable as 0.44 ± 0.10 MPa and 0.57 ± 0.18 MPa for native and hybrid aorta samples, respectively, while elongation at break (ɛ) values were 261% ± 17%, 7.5% ± 0.57%, and 22.18% ± 2.48% for wet control (native), decellularized dried aortae, and hybrid matrices, showing elastic contribution. Young's modulus data indicate that there was a threefold decrease in stiffness compared to decellularized samples once PGS is introduced into the ECM structure. Scanning electron microscopy (SEM) analysis of hybrid grafts revealed that the construct preserves porosity in medial layer of the vessel. Biocompatibility analyses showed no cytotoxic effects on human abdominal aorta smooth muscle cells. Cell studies showed 98% activity in hybrid graft extracts. As a control, collagen coating of the hybrid grafts was performed in the recellularization stage. SEM analysis of recellularized hybrid grafts revealed that cells were attached to the surface of the hybrid graft and proliferated during the 14 days of culture in both groups. This study shows that introducing an elastomer into the native ECM structure following decellularization process can be a useful approach for the preparation of mechanically enhanced composites for soft tissues.

New hybrid matrices for the synthesis of ion-exchange resins. The impact of the synthesis procedure on their porosity, functionalization and sorption of noble metals

ABSTRACTIn the search for new polymeric supports for the synthesis of ion-exchange resins, a new method has been assessed. A series of core-shell-type polymeric supports, based on the Amberlite XAD-4 adsorbent and vinylbenzyl chloride-divinylbenzene copolymer, has been obtained. The polymers, characterized by a diversified porous structure, were assessed by their functionalization into anion exchangers and their ability to remove Au(III), Pt(IV) and Pd(II).The efficiency of functionalization using ethylenediamine, as well as sorption capacity, was compared to the textural parameters of the initial supports, defining methods and techniques that will allow materials characterized by the most efficient usage of the vinylbenzyl chloride (VBC) monomer to be obtained.

Bacterial-biofilm enhanced design for improved electrocatalytic reduction of oxygen in neutral medium

The specific reactivity and ability of biofilms to form stable polymer-like hydrogel aggregates of microorganisms adhering to common solid (including the glassy carbon electrode) surfaces have been explored here to form systems analogous to electrocatalytic redox-polymer modified electrodes. Growth of biofilms has been demonstrated with use of Yersinia enterocolitica, a robust Gram-negative rod-shaped bacteria known to be resistive to pH changes (4-10) and temperature variations (0–40°C). Charge distribution and propagation within the biofilm have been enhanced by introduction of multi-walled carbon nanotubes. The fact that carbon nanotubes are derivatized with the carboxyl-group containing 4-(pyrrole-l-yl) benzoic acid has facilitated the hybrid material integrity and stability, namely through electrostatic attractive interactions between anionic carboxyl sites and positively charged domains of bacterial aggregates. In neutral media, the biofilm-based composite (hybrid) matrices have exhibited themselves electrocatalytic activity during electroreductions of oxygen and hydrogen peroxide (with possibility of its sensing in a broad range of concentrations). By immobilizing additional catalytic (cobalt porphyrin) sites, a truly bifunctional redox-polymer-like electrocatalytic system capable of significantly enhancing oxygen reduction currents has been produced. Apparently, the reduction of oxygen (to hydrogen peroxide) is initiated at cobalt porphyrin centers, and the second step (decomposition of hydrogen peroxide intermediate to water) is pursued at reactive sites (perhaps c-cytochrome) existing within biofilm matrix. Comparative measurements have been performed with the biofilm-supported platinum nanoparticles as well as with such a model catalytic system as platinized carbon nanotubes. The proposed electrode designs are relevant to biosensing and to the development of alternate cathode materials for biofuel cells or biobatteries.

Hybrid matrices of ZnO nanofibers with silicone for high water flux photocatalytic degradation of dairy effluent

Zinc oxide (ZnO) nanofibers were produced by electrospinning technique and surface coated on silicone elastomer substrate (diameter: 10.0 mm; thickness: 2.0 mm) by a dipcoating method. The obtained hybrid nanoporous matrices were investigated by scanning and transmission electron microscopy (SEM, TEM), X-ray diffraction (XRD) and Fourier transformation infrared techniques (FTIR). These characterizations reveal that the surface morphology of electrospun nanofibers remained intact by the dipcoating technique. The produced hybrid matrices showed high water flux of 9407 L/m2h, 38% removal rate of dairy effluent (DE) and 2298 ml/g h rate of hydrogen production.

Biomimetic mineralization of recombinant collagen type I derived protein to obtain hybrid matrices for bone regeneration.

Understanding the mineralization mechanism of synthetic protein has recently aroused great interest especially in the development of advanced materials for bone regeneration. Herein, we propose the synthesis of composite materials through the mineralization of a recombinant collagen type I derived protein (RCP) enriched with RGD sequences in the presence of magnesium ions (Mg) to closer mimic bone composition. The role of both RCP and Mg ions in controlling the precipitation of the mineral phase is in depth evaluated. TEM and X-ray powder diffraction reveal the crystallization of nanocrystalline apatite (Ap) in all the evaluated conditions. However, Raman spectra point out also the precipitation of amorphous calcium phosphate (ACP). This amorphous phase is more evident when RCP and Mg are at work, indicating the synergistic role of both in stabilizing the amorphous precursor. In addition, hybrid matrices are prepared to tentatively address their effectiveness as scaffolds for bone tissue engineering. SEM and AFM imaging show an homogeneous mineral distribution on the RCP matrix mineralized in presence of Mg, which provides a surface roughness similar to that found in bone. Preliminary in vitro tests with pre-osteoblast cell line show good cell-material interaction on the matrices prepared in the presence of Mg. To the best of our knowledge this work represents the first attempt to mineralize recombinant collagen type I derived protein proving the simultaneous effect of the organic phase (RCP) and Mg on ACP stabilization. This study opens the possibility to engineer, through biomineralization process, advanced hybrid matrices for bone regeneration.

A Conductive Hybridization Matrix of RuO2 Two‐Dimensional Nanosheets: A Hybrid‐Type Photocatalyst

AbstractA universal methodology to efficiently improve the photocatalyst performance of semiconductors was developed by employing exfoliated RuO2 two‐dimensional nanosheets as a conducting hybridization matrix. The hybridization with a RuO2 nanosheet is easily achieved by crystal growth or electrostatically derived anchoring of semiconductor nanocrystals on the RuO2 nanosheet. An enhanced chemical interaction of inorganic semiconductor with hydrophilic RuO2 nanosheet is fairly effective in optimizing their photocatalytic activity and photostability by the enhancement of charge separation and charge mobility. The RuO2‐containing nanohybrids show much better photocatalyst functionalities than do the graphene‐containing ones. The present study clearly demonstrates that hydrophilic RuO2 nanosheets are superior hybridization matrices, over the widely used hydrophobic graphene nanosheets, for exploring new efficient hybrid‐type photocatalysts.

A Conductive Hybridization Matrix of RuO2 Two-Dimensional Nanosheets: A Hybrid-Type Photocatalyst.

A universal methodology to efficiently improve the photocatalyst performance of semiconductors was developed by employing exfoliated RuO2 two-dimensional nanosheets as a conducting hybridization matrix. The hybridization with a RuO2 nanosheet is easily achieved by crystal growth or electrostatically derived anchoring of semiconductor nanocrystals on the RuO2 nanosheet. An enhanced chemical interaction of inorganic semiconductor with hydrophilic RuO2 nanosheet is fairly effective in optimizing their photocatalytic activity and photostability by the enhancement of charge separation and charge mobility. The RuO2 -containing nanohybrids show much better photocatalyst functionalities than do the graphene-containing ones. The present study clearly demonstrates that hydrophilic RuO2 nanosheets are superior hybridization matrices, over the widely used hydrophobic graphene nanosheets, for exploring new efficient hybrid-type photocatalysts.

Conducting-Polymer-Supported Bacterial Biofilms As Active Matrices for Noble Metal and Molecular Catalytic Centers: Enhancement of Electroreduction of Oxygen and Carbon Dioxide

Hybrid matrices composed of porous conducting polymer - polyaniline (PANI) or poly(3,4- ethylenedioxythiophene) (PEDOT) - underlayer, robust bacterial biofilm and the multi-walled carbon nanotubes have been demonstarted to function as highly active supports for dispersed catalztic centers (both noble metal nanoparticles and molecular ligand complexes). We explore unique properties of biofilms, i.e. polymeric aggregates of microorganisms, in which cells adhere to each other on the electrode surfaces. Such systems are characterized by extracellular electron transfers involving c-type cytochromes (heme-containing proteins). Biofilms grown on inert carbon electrode substrates tend to exhibit electrocatalytic properties towards oxygen and hydrogen peroxide reductions in neutral media. The processes have been found to be further enhanced by introduction of multi-walled carbon nanotubes (MCNTs) that are modified with ultra-thin layers of organic (e.g. 4-(pyrrole-l-yl) benzoic acid. We expect here attractive electrostatic interactions between carboxyl-group containing anionic adsorbates and positively charged domains of the biofilm with c-type cytochrome enzymatic sites. Coexistence of the above components leads to synergistic effect that is evident from positive shift of the oxygen reduction voltammetric potentials and significant increase of voltammetric currents. Most likely, the reduction of oxygen has been initiated at the molecular (e.g. intentionally added cobalt porphyrin redox centers), whereas the undesirable hydrogen peroxide intermediate are further decomposed at the cytochrome sites. Among other important observations is the significant enhancement of activity of Pt nanoparticles toward electroreduction of carbon dioxide in the presence of such a robust bacterial biofilm as Y. enterocolitica. Although interactions between platinum and such a complex ecosystem as biofilm are difficult to describe precisely, it is reasonable to postulate some inhibition of the hydrogen evolution (competitive reaction) at platinum nanoparticles in presence of bacterial microcolonies in favor of enhancement of the CO2-reduction. It is also noteworthy that biofilms are highly hydrated, and existence of open water channels between the bacterial microcolonies facilitates flow of supporting electrolyte. Combination of the hydrophobic polymer (PANI) structures with hydrophilic bacterial aggregates seems to produce attractive hybrid supports for electrocatalysts operating in aqueous media. Based on numerous repetitive diagnostic experiments in both argon and carbon dioxide saturated electrolytes, it can be stated that, by growing and supporting the biofilm onto the PANI polymer underlayer, the overall stability of the biofilm-based system has been improved. Indeed, we have not effectively observed any degradation of the hybrid catalytic films (both in terms of electrocatalytic activity and physicochemical stability) during our prolonged diagnostic experiments. Because measurements have been performed in neutral (phosphate buffer at pH=6.1) rather than acid medium, the PANI films (regardless of the presence of some HSO4 - anions) are not expected to be very well conducting. Consequently, we have also introduced MWCNTs to the electrocatalytic interface to facilitate charge distribution there.

A chemical approach to control the refractive index of sol–gel matrices for liquid-crystal dispersion devices

Devices based on gel-glass-dispersed liquid crystals (GDLC) were synthesized and assembled comprising 4-n-pentyl-4′-cyanobiphenyl (5CB) and hybrid organosilica–titania matrices obtained with sol–gel processes. The refractive index of the host matrices was modified by tailoring the chemical composition of the sol with appropriate mixtures of silicon and titanium alkoxide precursors. The chemical reactivity of the titanium–alkoxide precursor (titanium tetraisopropoxide) toward hydrolysis was controlled with a chelating agent (ethyl acetylacetonate) and a non-hydrolytic sol–gel process. Measurements of transmitted visible spectra of thin films deposited on glass substrates with spin coating yielded data on the refractive indices of the synthesized matrices. The operation of the GDLC devices was tested with a laser optical system; hybrid matrices having a refractive index similar to the ordinary refractive index of the LC produced the best results: up to 74 % transmittance applying an alternating voltage 30 V.

Hemicelluloses/montmorillonite hybrid films with improved mechanical and barrier properties.

A facile and environmentally friendly method was introduced to incorporate montmorillonite (MMT) as an inorganic phase into quaternized hemicelluloses (QH) for forming hemicellulose-based films. Two fillers, polyvinyl alcohol (PVA) and chitin nanowhiskers (NCH), were added into the hemicelluloses/MMT hybrid matrices to prepare hybrid films, respectively. The hybrid films were nanocomposites with nacre-like structure and multifunctional characteristics including higher strength and good oxygen barrier properties via the electrostatic and hydrogen bonding interactions. The addition of PVA and NCH could induce changes in surface topography, and effectively enhance mechanical strength, thermal stability, transparency, and oxygen barrier properties. The tensile strengths of the composite films FPVA(0.3), FPVA(0.5), and FNCH(0.8) were 53.7, 46.3, and 50.1 MPa, respectively, which were 171%, 134%, and 153% larger than the FQH-MMT film (19.8 MPa). The tensile strength, and oxygen transmission rate of QH-MMT-PVA film were better than those of quaternized hemicelluloses/MMT films. Thus, the proper filler is very important for the strength of the hybrid film. These results provide insights into the understanding of the structural relationships of hemicellulose-based composite films in coating and packaging application for the future.