Langmuir monolayer and Langmuir–Blodgett films of amphiphilic triblock copolymers with water-soluble middle block

Langmuir monolayers and Langmuir–Blodgett (LB) film morphology of amphiphilic triblock copolymers are studied using surface pressure-area measurements and atomic force microscopy (AFM), respectively. The triblock copolymers are composed of long water-soluble poly(ethylene oxide) (PEO) chains as middle block with very short poly(perfluorohexylethyl methacrylate) (PFMA) end blocks. The surface pressure-area isotherms show phase transitions in the brush regime. This phase transition is due to a rearrangement of PFMA block at the air–water interface. It becomes more significant with increasing PFMA content in the copolymer. LB films transferred at low surface pressures from the air–water interface to hydrophilic silicon substrates show surface micelles in the size range of 50–100 nm. A typical crystalline morphology of the corresponding PEO homopolymer is observed in LB films of copolymers with very short PFMA blocks, transferred in the brush region at high surface pressure. This crystallization is hindered with increasing PFMA content in the copolymer.     

Sol–gel preparation and properties of hydroxypropylcellulose–titania hybrid thin films

Hydroxypropylcellulose (HPC)–titania hybrid thin films were prepared by sol–gel method where titanium tetraisopropoxide Ti(OC₃H₇ ⁱ )₄ was hydrolyzed under acidic conditions in the presence of HPC, followed by dip-coating and drying at 120 °C for 24 h. The viscosity average molecular weight of HPC was 55,000–70,000 or 110,000–150,000, and the TiO₂/(HPC + TiO₂) mass ratio ranged from 0 to 1, which was calculated on the assumption that all Ti(OC₃H₇ ⁱ )₄ is converted into TiO₂. The films were 0.35–1.0 μm thick, transparent in visible region and opaque in ultraviolet (UV) region, where the optical absorption coefficient in UV region increased with increasing titania content. The refractive index increased with increasing titania content, ranging from 1.6 to 1.8 for the hybrid thin films. The pencil hardness increased from 6B to 5H, the durability in hot water significantly increased and the contact angle of water on films increased from 35° to 89° with increasing titania content. Crack-free films could be deposited on organic polymer substrates irrespective of titania or HPC contents, where cracking did not occur at higher HPC contents even when the substrate was bent.     

In situ fabrication of polyacrylate/nanozirconia hybrid material via frontal photopolymerization

Frontal photopolymerization was applied to fabricate polymer/nanozirconia hybrid material by using acrylates as polymerizable components and tetrabutyl zirconate (TBZ) as the precursor of nanozirconia, respectively. The nanozirconia particles were in-situ generated with the polymerization front traveling and gradiently dispersed in the simultaneously formed polymer rod. The iodonium salt was utilized as photoacid generator to produce protonic acid and drive TBZ into nanozirconia particles. With the frontal polymerization traveling downward, the particle size and concentration of zirconia increased, but layer-resolved conversion of TBZ decreased. The particle size of zirconia could be reduced remarkably by the protection of monoalkyl titanate bearing six long chains. The refractive index of the hybrid rod was found to increase from top to down. The top–down layer-resolved storage modulus of the hybrid rod increased due to nanoparticle filling effect but decreased beyond the depth of 4 cm from the top, which may be ascribed to particle aggregation. This project is supported by the National Natural Science Foundation of China (grant no. 20304019, 60378029).     

Optical,electrical, and thermochromic properties of polyazothiophene Langmuir–Blodgett films

The conductivity and luminescence of conjugated polymers may be combined with the photoisomerization capability of azobenzene materials to achieve unique properties for a variety of applications, particularly if conjugated polymers with azobenzene side chains are processed as nanostructured films. In this study, we report on Langmuir–Blodgett (LB) films of a polythiophene-bearing azobenzene moieties, which displayed photoluminescence, thermochromism, electroactivity, and photoinduced birefringence. The latter three properties were enhanced in the LB films, as compared to spin-coated films of the polyazothiophene, and this has been attributed to differences in film morphology that could be probed with atomic force microscopy.     

Electrochemical charging and electrocatalysis at hybrid films of polymer-interconnected polyoxometallate-stabilized carbon submicroparticles

Using the layer-by-layer technique, carbon submicroparticles, that have been modified and stabilized with monolayers of Keggin-type phosphododecamolybdate (PMo₁₂O₄₀³⁻), can be dispersed in multilayer films of organic polymers, poly(3,4-ethylenedioxythiophene), i.e., PEDOT, or poly(diallyldimethylammonium) chloride, i.e., PDDA, deposited on glassy carbon or indium-tin oxide conductive glass electrodes. The approach involves alternate treatments in the colloidal suspension of PMo₁₂O₄₀³⁻-covered carbon submicroparticles in the solution of monomer, 3,4-ethylenedioxythiophene or in solution of PDDA polymer. Electrostatic attractive interactions between anionic phosphomolybdate-modified carbon submicroparticles and cationic polymer layers permit not only uniform and controlled growth of the hybrid organic–inorganic film but also contribute to its overall stability. The system composed of PMo₁₂O₄₀³⁻-covered carbon submicroparticles dispersed in PEDOT is characterized by fast dynamics of charge transport and has been used to construct symmetric microelectrochemical redox capacitor. The PDDA-based system has occurred to be attractive for electrocatalytic reduction of hydrogen peroxide.     

A zirconia-polyester glycol coating on differently pretreated AISI 316L stainless steel: corrosion behavior in chloride solution

The effect of zirconia and zirconia-polyester glycol hybrid coatings on the corrosion resistance of mechanically polished or anodized AISI 316 stainless steel (316L), was studied by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.1 M NaCl and scanning electron microscope and atomic force microscopy examinations. The deposition of zirconia coatings was achieved by the sol–gel technique by immersing the samples in either the inorganic polymer or the organic–inorganic polymer mixture. From potentiodynamic and impedance measurements, the grade of protection is reduced with the exposure time to the electrolyte, which is mainly associated with lost of film adhesion and, consequently, detachment from the metal substrate. However, the uncoated anodized sample revealed an unexpected corrosion behavior; the anodic film formed during anodizing readily increased the corrosion resistance of the 316L stainless steel in 0.1 M NaCl, revealing a considerable reduction in the corrosion current density and an increase in the pitting potential.     

Hydrothermal Synthesis and Structural Characterization of Two Organic–Inorganic Hybrids Based on Sandwich-type Polyoxometalates

Abstract  Two novel inorganic–organic hybrid sandwich-type phosphotungstates [H₂en][Ni(en)₂]₂[{(α-B-PW₉O₃₄)₂Ni₄(H₂O)₂}{Ni(en)₂(H₂O)}₂] · 5H₂O (1) and [Ni(en)₂][Ni(en)₂(H₂O)₂][{(α-B-PW₉O₃₄)₂Ni₄(Hen)₂}{Ni(en)₂(H₂O)}₂] · 10H₂O (2) (en = ethylenediamine) have been synthesized by the hydrothermal reactions of trivacant precursors Na₉[α-A-PW₉O₃₄] · 7H₂O/Na₁₂[α-P₂W₁₅O₅₆] · 18H₂O with NiCl₂ · 6H₂O in the presence of en and structurally characterized by IR spectra, elemental analyses and thermogravimetric analyses. X-ray crystallographic analyses indicate that 1 is made up of inorganic polyoxoanions [Ni₄(H₂O)₂(α-B-PW₉O₃₄)₂]^10– decorated by nickel-organoamine groups, while 2 is constructed from inorganic–organic hybrid polyoxoanions [(α-B-PW₉O₃₄)₂Ni₄(Hen)₂]^8– decorated by nickel-organoamine groups. Graphical Abstract   Hydrothermal Synthesis and Structural Characterization of Two Organic–Inorganic Hybrids based on Sandwich-type Polyoxometalates Bing Li, Zhao Dan, Shou-Tian Zheng, Guo-Yu Yang      

Dicyanopyrazine-linked porphyrin Langmuir-Blodgett films

We investigated the influence of arachidic acid/cadmium dication (AA/Cd(2+)) as a transfer promoter for the deposition of dicyanopyrazine-linked porphyrin (2-DCPP) Langmuir-Blodgett (LB) films on both hydrophobic and hydrophilic substrates. In the case of LB deposition on a hydrophilic substrate, the presence of AA/Cd(2+) does not improve 2-DCPP LB deposition. The poor transfer in the case of the hydrophilic surface is believed to be due to 2-DCPP not wetting the surface during the down-stroke deposition, and this is not improved by the transfer agent. However, on a hydrophobic substrate, deposition of 2-DCPP is significantly improved by the presence of AA/Cd(2+). Comparison of the UV-visible spectrum of a 2-DCPP LB film with that of 2-DCCP dissolved in chloroform reveals that the Soret and Q bands for the 2-DCPP LB film are broadened and red-shifted due to aggregation of porphyrin rings in the LB film. UV-visible spectral changes and ellipsometry as a function of the number of deposition layers suggest continuous transfer of 2-DCPP/AA onto the hydrophobic substrate and reproducibility in the deposition process. The Soret and Q bands of the 2-DCPP LB film upon acid vapor exposure have also been investigated, and these measurements may have chemical sensor applications.     

UV curing of organic–inorganic hybrid coating materials

The effect of UV-curing time on the mechanism of interaction between the various precursor phases in a novel sol–gel-derived organic–inorganic hybrid coating material and the resulting mechanical and thermal properties of this material when coated onto substrates in thin film form have been examined using a variety of chemical and physical characterisation methods. Microstructurally, the hybrid coating materials examined were all a single amorphous phase and were all optically transparent. The degree of interaction between the organic and inorganic phases, the scratch behaviour of the coating materials and the thermal stability of the coating materials were all found to depend strongly on the UV curing time. For the particular proportions of inorganic and organic components used to make up this hybrid coating material, an optimum UV curing time of 10 min under a UV intensity of 46.3 mW cm⁻² was found to produce transparent coatings which adhered well to the substrates and which were robust in scratch tests on aluminium and polycarbonate substrates and abrasion tests on polycarbonate substrates.     

Sol–gel derived hybrid coatings for the improvement of scratch resistance of polyethylene

Organic–inorganic hybrid materials were prepared through the sol–gel approach starting from tetraethoxysilane (TEOS), as silica precursor, and triethoxysilane terminated polymers; before gelling the solutions were applied to polyethylene (PE) films and slabs by spin-coating, without any previous surface pre-treatment of the substrate, and finally the coatings were thermally cured at 60 °C for 24 h. Among the various polymers used to prepare the coatings, only polyethylene-b-poly(ethylene glycol) copolymers gave good results in terms of adhesion to the PE substrates, and hybrid coatings with different organic–inorganic ratios were prepared. As suggested by visual inspection and SEM investigation, and confirmed by the critical loads derived from scratch tests, a good adhesion of the coating to the PE substrates was obtained, probably due to the presence of PE segments in the organic phase of the coating. Transparency as well as SEM and DSC data were in agreement with the formation of a nanostructured hybrid coating, with a high level of interpenetration between organic and inorganic domains. It was also observed that these hybrid coatings are able to improve significantly the scratch resistance and slightly increase the wettability with respect to uncoated PE. This approach to the surface-properties modification of PE appears as a simple and convenient method for the functionalization of PE substrates.     

High transparent thermal curable hybrid polycarbonate films prepared by the sol–gel method

Polycarbonate/epoxy/silica hybrid films were prepared by curing an epoxy reaction via in situ sol–gel process. The influence of the synthetic conditions, such as the ratio of different epoxy reagents and the contents of [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane on the physical and optical properties of these hybrid films were investigated in details. The coefficient of thermal expansion, surface roughness, and light transmittance at a wavelength range from 250 to 800 nm were measured. These excellent overall performances make it a promising photonic packaging material.     

Comparative study of different indigo-clay Maya Blue-like systems using the voltammetry of microparticles approach

Using the voltammetry of microparticles approach, the electrochemical response of complexes prepared with indigo plus different clays in contact with aqueous electrolytes is described. Indigo presents a strong attachment with palygorskite and sepiolite in contrast to a weak attachment to planar clays (montomorillonite and kaolinite). Cyclic voltammetric and chronoamperometric data provide estimates of the variation of the concentration of indigo and dehydroindigo with the depth on clay crystals. The indigoids (indigo and dehydroindigo) penetrate more in palygorskite than in sepiolite, and this penetration is favoured by thermal treatments (very efficient up to 130 °C). The indigo concentration decreases monotonically versus depth, while the dehydroindigo one increases from zero in the external region of the crystals to a maximum at a depth between 40 and 80 nm and then decreasing rapidly. These facts are directly linked to the much higher resistance to acid attack of palygorskite–indigo pigments (Maya Blue) than sepiolite–indigo ones.     

Periodic Mesoporous Silicas and Organosilicas: An Overview Towards Catalysis

Micelle-templated mesoporous and organic–inorganic hybrid mesoporous materials are important in many fields of material research, especially for hosting catalysts in confined space. Among this class, the recent discovery of periodic mesoporous organosilicas (PMOs) represent an exciting new group of organic–inorganic nanocomposites targeted for a broad range of applications ranging from catalysis to microelectronics. Compared to the earlier generation of organic–inorganic hybrid mesoporous samples, obtained by the cocondensation reaction or by the grafting reaction, PMOs represent the right combination of organic and inorganic groups in the frame wall positions. This article reviews the current state of art in organic–inorganic hybrid mesoporous material research with special emphasis over periodic mesoporous organosilica materials having various redox centers (Ti, V, Cr) suitable for oxidation reactions as well as acidic sites (Al, –SO₃H) for the organic transformation of bulky molecules.     

Two Novel 1-D Organic–Inorganic Composite Phosphotungstates Constructed from [Ln(α-PW11O39)2]11− Units and [Cu(en)2]2+ Bridges (Ln = CeIII/ErIII)

Abstract  Two novel organic–inorganic composite phosphotungstates, [H₉{Ce(α-PW₁₁O₃₉)₂}Cu(en)₂] · 6H₂O (1) and H₇[Cu(en)₂{Er(α-PW₁₁O₃₉)₂}Cu(en)₂] · 12H₂O (2) (en = ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [α-A-PW₉O₃₄]⁹⁻ with Ce^III or Er^III ions in the presence of Cu²⁺ ions and en, and structurally characterized by IR spectra, elemental analysis and thermogravimetric analysis. X-ray crystallographic analyses indicate that they are all built by sandwich-type [Ln(α-PW₁₁O₃₉)₂]¹¹⁻ (Ln = Ce^III, Er^III) polyoxoanions and [Cu(en)₂]²⁺ cations generating infinite one-dimensional arrangements. To our knowledge, this 1-D chain structures constituted by mono-Ln sandwiched POM units and transition-metal complex cations are very rare. Graphical Abstract  Two novel organic–inorganic composite phosphotungstates, [H₉{Ce(α-PW₁₁O₃₉)₂}Cu(en)₂] · 6H₂O (1) and H₇[Cu(en)₂{Er(α-PW₁₁O₃₉)₂}Cu(en)₂] · 12H₂O (2) (en = ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [α-A-PW₉O₃₄]⁹⁻ with Ce^III or Er^III ions in the presence of Cu²⁺ ions and en, and structurally characterized by IR spectra, elemental analysis and thermogravimetric analysis. X-ray crystallographic analyses indicate that they are all built by sandwich-type [Ln(α-PW₁₁O₃₉)₂]¹¹⁻ (Ln = Ce^III, Er^III) polyoxoanions and [Cu(en)₂]²⁺ cations generating infinite one-dimensional arrangements. To our knowledge, this 1-D chain structures constituted by mono-Ln sandwiched POM units and transition-metal complex cations are very rare.      

Novel Hybrids Constructed from Keggin-Polyoxometalate and Mixed Copper Complex

Abstract  Two new Keggin-polyoxometalate hybrids, {[Cu₂(4,4′-bpy)₂][PW₁₀^VIW₂^VO₄₀]}[Cu₂(obpy)₂]₄ · 2 H₂O (1) and {[Cu₄(2,2′-bpy)₄(4,4′-bpy)₃][SiW₁₂O₄₀]} · 2H₂O (2) (4,4′-/2,2′-bpy = 4,4′-/2,2′-bipyridyl, Hobpy = 6-hydroxy-2,2′-bipyridyl), were hydrothermally synthesized and structurally characterized. Gillard type hydration of 2,2′-bipy is observed during the synthesis of 1, resulting in a new obpy ligand in situ. X-ray structural analyses show that 1 consists of 1D hybrid chain {[Cu₂(4,4′-bpy)₂][PW₁₀^VIW₂^VO₄₀]}_∞ and [Cu₂(obpy)₂] dimer, whereas 2 possesses 1D hybrid structure based on Keggin-type [SiW₁₂O₄₀]⁴⁻ anions and tetra-nuclear copper complexes [Cu₄(2,2′-bpy)₄(4,4′-bpy)₃]⁴⁺. Both compounds present interesting supramolecular architectures based on π–π stacking and hydrogen bonds. Graphical Abstract  Compounds {[Cu₂(4,4′-bpy)₂][PW₁₂O₄₀]}[Cu₂(obpy)₂]₄ · 2H₂O (1) and [Cu₄(2,2′-bpy)₄(4,4′-bpy)₃][SiW₁₂O₄₀] · 2H₂O (2) were hydrothermally synthesized. 1 features that the [Cu₂(obpy)₂] dimers based on in situ generated obpy ligands are stumped between the layers where 1D hybrid chain {[Cu₂(4,4′-bpy)₂][PW₁₂O₄₀]}_∞ locates, while 2 exhibits 1D chain-like structure based on anions [SiW₁₂O₄₀]⁴⁻ and tetra-copper complexes [Cu₄(2,2′-bpy)₄(4,4′-bpy)₃]⁴⁺.      

Studies on the oxygen sensitivity and microstructure of sol–gel based organic–inorganic hybrid coatings doped with platinum porphyrin dye

Hybrid organic–inorganic nanocomposite coatings were prepared by copolymerizing tetraethylorthosilicate with ethyltriethoxysilane with an acid catalysis process. Oxygen sensor coatings were fabricated by doping the hybrid sol with platinum meso-tetra(pentfluorophenyl) porphyrin. Photophysical properties and oxygen sensitivity of the sensor coatings were studied. The microstructure of the coatings was examined using optical microscopy and scanning electron microscopy. The effect of sol–gel process conditions like precursor silane molar ratio, acid concentration and stirring time of the sol on the oxygen sensitivity and surface microstructure of the sensor coating was studied. Oxygen sensitivity and surface morphology of the coatings were dependent on the sol–gel process parameters.     

Synthesis, structure and spectroscopic characterization of a new organic cation diphosphate: [2,6-(C2H5)2C6H3NH3]2H2P2O7?·?2H2O

The chemical preparation, crystal structure and spectroscopic characterization of [2,6-(C₂H₅)₂C₆H₃NH₃]₂H₂P₂O₇ · 2H₂O have been reported. The compound crystallizes in the monoclinic system in space group P2₁/c and cell parameters a = 14.323(2), b = 11.158(3), c = 16.387(2) ? and β = 96.34(3)°; V = 2602.8(9) ?³ and Z = 4. Crystal structure has been determined and refined to R = 0.044, using 3528 independent reflections. The atomic arrangement of the title compound shows anionic layer of formulae [H₂P₂O₇(H₂O)₂] _n ²ⁿ⁻ stacked along the c-axis. The 2,6-diethylanilinium cations establish on both sides of these inorganic layer hydrogen bonds so as to contribute to the intralayer cohesion in the network. The different building species are held together by means of O–H···O and N–H···O intermolecular hydrogen bonds in addition to electrostatic and van der Waals interactions.     

Synthesis of maleimide substituted polystyrene–silica hybrid utilizing michael addition reaction

The transparent polymer hybrids were prepared from polystyrene bearing pendant maleimide moieties (16%) and tetraethoxysilane (TEOS) using γ-aminopropyltriethoxysilane (γ-APS) as a crosslinking agent by an in situ sol–gel process by utilizing Michael-addition reaction. Maleimide substituted polystyrene was synthesized by a mild Friedel-Crafts reaction of polystyrene and N-chloromethylmaleimide. Fourier Transform Infrared (FTIR) spectral data confirms the occurrence of Michael-addition reaction between the pendant maleimide moieties of the styrene copolymer and γ-aminopropyltriethoxysilane. The percentage of maleimide substitution was calculated from ¹H NMR spectrum. The transparent hybrid shows high solvent resistance at the boiling point of Tetrahydrofuran (THF) since the polystyrene-substituted-maleimide (PS-s-MA) was covalently bonded with siloxane matrix. Thermal properties of the transparent hybrid materials were investigated by Differential scanning calorimeter (DSC) and Thermo gravimetric analysis (TGA) in order to ascertain their glass transition temperature (Tg) and thermal stability behaviour. Morphology and transparency of the organic–inorganic hybrids were confirmed by Scanning electron microscopy (SEM) and optical images. The homogeneity of the polymer hybrids was also examined by nitrogen porosimetry studies.     

Photoelectrical properties of Langmuir–Blodgett films of poly(methyl phenylsilane)s

Langmuir–Blodgett (LB) films were prepared from poly(methylphenylsilane) bearing electron acceptor π-conjugated substituents. The small limiting area (0.078 nm²) per one repeating unit of polysilane (PSi) in monomolecular film and the large thickness of the film (6 nm) suggest that the polymer chains are not fully spread on water surface. The electrical and photoelectrical properties of Al/LB film/Au sandwich cells containing various numbers of the polysilane layers were studied. Holes were transported from the Al electrode through the LB film to the Au electrode when the light was absorbed by the polysilane. The highest photovoltaic effect occurred in the first monolayer of polysilane at the Al contact. The cell resistivity and the photovoltage were decreased by parallel conductance of defects in the films consisting of small numbers of PSi layers.     

Synthesis,characterization and performance of nanosized Bi<Subscript>0.1</Subscript>Sn<Subscript>0.9</Subscript>O<Subscript>2</Subscript>–WPU organic–inorganic hybrid coatings

A series of organic–inorganic hybrid coatings consisting of organic waterborne polyurethane (WPU) and inorganic nanosized bismuth-doped tin dioxide were successfully synthesized by the in situ polymerization approach. Bi_0.1Sn_0.9O₂ nano-powders were prepared via a new route of sol–gel combustion hybrid method using acetylene black as the fuel. The formed nano-powders were characterized by transmission electron microscopy and X-ray diffraction (XRD). Bi_0.1Sn_0.9O₂–WPU was then fabricated with isophorone diisocyanate, 2,2-bis(hydroxymethyl) propionic acid and nano-Bi_0.1Sn_0.9O₂-poly(ε-caprolactone) (PCL) as the starting materials. Organic–inorganic hybrid coatings are always achieved with adjustable contents of Bi_0.1Sn_0.9O₂. The hybrid coatings with Bi_0.1Sn_0.9O₂ loading on the glass substrate exhibited good heat insulation efficiency. The tensile strength and breaking extensibility of nanocomposite film containing 1.0% of the nano-Bi_0.1Sn_0.9O₂ were measured as 9.35 MPa and 248%, respectively. The transmittance of visible light was above 80%. The heat insulation of glass coated with nano-Bi_0.1Sn_0.9O₂–WPU hybrid was over 60 °C in contrast to the commercial blank glass.