Inorganic/organic nanocomposite coatings: The next step in coating performance

Inorganic/organic hybrid materials have considerable promise and are beginning to become a major area of research for many coating usages, including abrasion and corrosion resistance. Our primary approach is to prepare the inorganic phase in situ within the film formation process of the organic phase. The inorganic phase is introduced via sol-gel chemistry into a thermosetting organic phase. By this method, the size, periodicity, spatial positioning, and density of the inorganic phase can be controlled. An important aspect of the inorganic/organic hybrid materials is the coupling agent. The initial task of the coupling agent is to provide uniform mixing of the oligomeric organic phase with the sol-gel precursors, which are otherwise immiscible. UV-curable inorganic/organic hybrid systems have the advantages of a rapid cure and the ability to be used on heat sensitive substrates such as molded plastics. Also, it is possible to have better control of the growth of the inorganic phase using UV curing. It is our ultimate goal to completely separate the curing of inorganic and organic phases to gain complete control over the morphology, and hence optimization of “all” the coating properties. Thus far, it has been found that concomitant UV curing of the inorganic and organic phases using titanium sol-gel precursors afforded nanocomposite coatings which completely block the substrate from UV light while maintaining a transparent to visible light. Also, it has been found that the morphology of the inorganic phase is highly dependent on the concentration and reactivity of the coupling agent. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago, IL.     

复合相变储热材料的研究与发展

系统概括和评述了复合相变材料的制备方法及其研究进展，并介绍了研制有机／无机纳米复合相变储热材料的创新思路及初步研究成果，提出，有机／无机纳米复合技术是制备高性能复合相变储热材料的新途径。     

溶胶-凝胶技术在有机／无机杂化材料制备中的应用

应用溶胶-凝胶法制备有机／无机杂化材料,可根据前驱体的种类和制备方法等对材料微观结构进行裁剪和优化,并可实现材料的功能化。有机／无机杂化材料根据有机相和无机相的比例不同,可分为有机改性陶瓷型杂化材料和陶瓷改性有机物型杂化材料两类。本文综述了应用溶胶-凝胶技术制备有机／无机杂化材料的原理以及应用进展。     

Direct Electrochemistry and Electrocatalysis of Hemoglobin on Bimetallic Au–Pt Inorganic–Organic Nanofiber Hybrid Nanocomposite and Mesoporous Molecular Sieve MCM-41

A glassy carbon electrode modified with MCM-41 and bimetallic inorganic–organic nanofiber hybrid nanocomposite was prepared and used for determination of trace levels of hydrogen peroxide (H₂O₂). The direct electron transfer (DET) and electrocatalysis of hemoglobin (Hb) entrapped in the MCM-41 modified Au–Pt inorganic–organic nanofiber hybrid nanocomposite electrode (Au–PtNP/NF/GCE) were investigated by using cyclic voltammetry in 0.1 M pH 7.0 phosphate buffer solution. Due to its uniform pore structure, high surface area and good biocompatibility, the mesoporous silica sieve MCM-41 provided a suitable matrix for immobilization of biomolecules. The MCM-41 modified Au–Pt inorganic–organic nanofiber hybrid nanocomposite electrode showed significant promotion to DET of Hb, which exhibited a pair of well-defined and quasi-reversible peaks for heme Fe(III)/Fe(II) with a formal potential of ?0.535 V (vs. Ag/AgCl). Additionally, the Hb immobilized on the MCM-41 modified electrode showed excellent electrocatalytic activity toward H₂O₂ reduction.     

二氧化硅核壳纳米材料的研究进展

核壳型纳米材料作为一种新型的复合型材料,在内核和外壳的协同作用下,能够发挥出单一材料或合金无法比拟的性能优势。根据组成材料属性的不同可以将核壳纳米材料分为无机/无机、无机/有机、有机/无机和有机/有机核壳材料4大类。介绍了核壳材料的形成机理,主要对以二氧化硅为外壳,以金属、金属氧化物、分子筛为内核的几种无机核壳材料的最新研究成果及应用进行了综述。最后,对核壳材料未来的发展前景进行了展望。     

Feasibility of in situ de-agglomeration during powder consolidation

Consolidation of nano-sized powders is a growing area in manufacturing of advanced materials, thanks to the reduced processing times, enhanced mechanical properties and high potential for the introduction of multi-functionality enabled by such reduced particle sizes. Nanopowders, however, are particularly prone to the agglomeration phenomena, and thus to the formation of hierarchical porous structures. The presence of pores differing up to several orders of magnitude in size leads to undesired differential shrinkage and localized grain growth. In order to avoid such issues, strategies for in situ de-agglomeration are proposed here. These optimization strategies are based on the development of an analytical model for shrinkage kinetics and mechanical properties of a hierarchical porous structure, containing both small-size intra-agglomerate pores and large-size inter-agglomerate ones. The modeling approach is an expansion of the continuum theory of sintering to the case of biporous materials presenting nonlinear viscous rheology, as expected for nano-sized crystalline powders. Considering the nonlinear viscous constitutive behavior of the solid phase also allows assessing the influence of the temperature on the microstructural evolution during processing, due to the dependence of the creep characteristic parameter, strain-rate sensitivity, on the thermal history. Material structure optimization strategies, aimed at de-agglomeration or at the design of tailored porous structures, become then possible and are here explored.     

Synthesis and cytocompatibility of collagen/hydroxyapatite nanocomposite scaffold for bone tissue engineering

Collagen/hydroxyapatite nanocomposite scaffolds were prepared by in situ precipitation and freeze‐drying approach. The synthesized collagen/hydroxyapatite nanocomposites were characterized using various modalities. It was revealed that the inorganic phase in the nanocomposite was carbonate‐substituted hydroxyapatite with low crystallinity. Morphology studies showed the uniform distribution of hydroxyapatite particles in the collagen hydrogel. In addition, hydroxyapatite particles were gradually becoming irregular enough and the surface morphology had more wrinkles with the increase of inorganic component. Morphology, mechanical properties and cell biocompatibility of the prepared nanocomposite scaffolds were evaluated. The scaffolds presented a well‐developed macropore structure with a pore size ranging from 100 to 200 μm and the pore size of scaffold can also be regulated by changing the organic/inorganic weight ratio. Furthermore, the growth of MG63 cells on scaffolds showed they could significantly promote the proliferation of cells and could be potential candidate for bone engineering applications. POLYM. COMPOS., 81–90, 2016. © 2014 Society of Plastics Engineers     

Organic-inorganic nanocomposite polymer electrolyte membranes for fuel cell applications

Organic-inorganic nanocomposite polymer electrolyte membrane (PEM) contains nano-sized inorganic building blocks in organic polymer by molecular level of hybridization. This architecture has opened the possibility to combine in a single solid both the attractive properties of a mechanically and thermally stable inorganic backbone and the specific chemical reactivity, dielectric, ductility, flexibility, and processability of the organic polymer. The state-of-the-art of polymer electrolyte membrane fuel cell technology is based on perfluoro sulfonic acid membranes, which have some key issues and shortcomings such as: water management, CO poisoning, hydrogen reformate and fuel crossover. Organic-inorganic nanocomposite PEM show excellent potential for solving these problems and have attracted a lot of attention during the last ten years. Disparate characteristics (e.g., solubility and thermal stability) of the two components, provide potential barriers towards convenient membrane preparation strategies, but recent research demonstrates relatively simple processes for developing highly efficient nanocomposite PEMs. Objectives for the development of organic-inorganic nanocomposite PEM reported in the literature include several modifications: (1) improving the self-humidification of the membrane; (2) reducing the electro-osmotic drag and fuel crossover; (3) improving the mechanical and thermal strengths without deteriorating proton conductivity; (4) enhancing the proton conductivity by introducing solid inorganic proton conductors; and (5) achieving slow drying PEMs with high water retention capability. Research carried out during the last decade on this topic can be divided into four categories: (i) doping inorganic proton conductors in PEMs; (ii) nanocomposites by sol-gel method; (iii) covalently bonded inorganic segments with organic polymer chains; and (iv) acid-base PEM nanocomposites. The purpose here is to summarize the state-of-the-art in the development of organic-inorganic nanocomposite PEMs for fuel cell applications.     

LBL技术制备有机/无机纳米复合薄膜研究进展

将高分子和各种功能的无机纳米粒子通过层层吸附自组装技术进行组装,制备厚度可控和稳定性好的有机/无机纳米复合薄膜。综述了该领域研究的最新进展,介绍了利用LBL技术制备有机/无机纳米复合薄膜的方法,并对利用LBL技术制备有机/无机纳米复合薄膜的发展趋势作了展望。     

Plant oil polyol nanocomposite for antibacterial polyurethane coating

Some preliminary investigations on “green” preparation, morphology and antibacterial behavior of Linseed polyol nanocomposite [LMPOL] for antibacterial polyurethane coatings are summarised. Nanocomposite is prepared in situ with Linseed polyol [LP] matrix as organic and Copper acetate as inorganic constituent by “solventless one-pot” chemical reaction. The presence of characteristic absorption bands in FTIR spectra confirmed the formation of LMPOL. TEM analysis showed the presence of nano-sized metal oxide in LMPOL. LMPOL showed good antibacterial behavior against E. coli and S. aureus. The interactions between LMPOL and bacterial surfaces lead to good antibacterial efficacy, suggesting membrane disruption based cell death. LMPOL may serve as an excellent starting material for antibacterial polyurethane coating. The approach is an excellent example for the preparation of “green” polyol from “green” resource en route Green Chemistry for protective polyurethane coatings.     

Structure and phase transition in thin films of block copolymer micelles complexed with inorganic precursors

Block copolymer micelle can be used as nano-reactor where separated domains serve as a compartment for the production of nanomaterials, ultimately creating nanocomposite materials. In this work, thin nanocomposite films generated from polystyrene-b-poly(acrylic acid) (PS-b-PAA) micellar solution in which small amount of inorganic precursor was added were investigated. The films were prepared by spin coating onto silicon substrate, and then solvent-annealed. As-spun films exhibit typical micellar structure with spherical shape along which inorganic nanoparticles are dispersed. Such morphology remains unchanged after solvent annealing for micellar films with small amount of inorganic precursor. However, further increase in the amount of inorganic precursors brings about the morphological changes, producing different organization of inorganic nanoparticles in composite films. This behavior was found to strongly depend on the types of precursors and solvents used for annealing. These results illustrate a simple yet useful route to generate the polymeric nanocomposites with diverse structure and composition.     

Characterization of a hybrid nano-silica waterborne polyurethane coating for clay bricks

A transparent hybrid organic–inorganic waterborne coating was evaluated for the protection of clay bricks. The nanocomposite film was prepared by combining an environmentally friendly process based on UV-curing of water-based acrylic resins and a mild thermal treatment to form nanosilica in situ from alkoxysilane precursors. Coated and uncoated facing bricks were compared by scanning electron microscopy, surface profilometry, water wettability, and capillary rise tests. The hybrid coatings act as a moderate water repellent; interestingly, no appreciable alteration of the aesthetic properties of the brick was observed, in particular no gloss or color change appeared after the treatment.     

Directed inorganic modification of bi-component polymer fibers by selective vapor reaction and atomic layer deposition

Nanocomposite organic/inorganic materials with spatially-controlled composition can be formed using vapor-phase atomic layer deposition (ALD) on bi-component polymer fibers. The ALD process promotes selective precursor infusion into the inner core of a core/shell polymer fiber, yielding nanoparticles encapsulated within the core. Likewise, choosing alternate precursors or reaction conditions yield particles or films on the outer polymer shell. In-situ infrared spectroscopy and transmission electron microscopy show that infusion yields selective dispersion of aluminum oxide in different polymer regions, forming fine nanoparticle dispersions or films. Selective inclusion of metal oxide materials during atomic layer deposition on polymers can create unique organic/inorganic composite structures for many advanced uses.     

Small angle neutron scattering study of the structure and formation of MCM-41 mesoporous molecular sieves

The nanoscale structure and synthesis mechanisms of the MCM-41 class of inorganic mesoporous materials have been investigated by small angle neutron scattering (SANS). SANS measurements with solvents imbibed in the pores to vary the scattering contrast demonstrate that the low angle diffraction peaks from these materials are entirely due to the pore structure and that the pores are fully accessible to both aqueous and organic solvents. Static and shear flow SANS measurements on the concentrated cationic surfactant and silicate precursor solutions typically used in the synthesis of the mesopore materials indicate that the existence of preassembled supramolecular arrays that mimic the final pore structure is not essential for the synthesis of these materials.     

多孔液体：合成与应用

多孔液体是一类具有永久孔隙的新兴液体材料,它将多孔材料优异的性能和液体的流动性结合在一起。具有永久空腔的造孔器（pore generator）,可以完全由无机砌块单元、有机配体和无机节点的组合单元或有机砌块单元构成。本文根据造孔器的结构综述了使用无机纳米材料、金属有机框架和多孔笼合成多孔液体的最新研究进展。文章指出作为新的研究领域,多孔液体化学正处于起步阶段,虽然面临着诸多挑战,但应用潜力巨大。目前在气体吸附、异构体识别、多孔液体膜的合成等方面都有研究,有望在气体捕捉和分离、催化、膜材料制备等领域得到应用。     

The influence of different carbon sources in the carbothermal reduction and nitridation (CRN) synthesis of SiAlON from nanocomposite precursors based on Al–SBA-15

Nanocomposites of Al–SBA-15 with the organic polymers poly-4-vinyl pyridine (P4VP) and polyacrylamide (PAM) were synthesized to produce SiAlON precursors containing various carbon contents. These CRN precursors, and their products after firing under N₂ at 1450 °C for 3 h were investigated by XRD, SEM/EDS and surface area analysis (BET) to compare the influence of the organic polymer carbon source. The results were also compared with those from precursors containing carbon black as the carbon source. XRD and SEM/EDS analysis of the Al–SBA-15 confirmed the formation of mesoporous structures, while BET and pore size distribution measurements indicated that the entry of P4VP into the Al–SBA-15 nanocomposite precursor is significantly more efficient than that of PAM. Firing these precursors in nitrogen produced β-SiAlON and β-cristobalite. At all carbon concentrations the P4VP nanocomposite precursors formed significantly more SiAlON than those of the PAM and carbon black precursors, due to the proximity of a greater amount of the organic carbon source to the silica template in the P4VP composite, and possibly also to the lack of oxygen in the P4VP monomer, in contrast with PAM. At least twice the stoichiometric amount of carbon was required in all cases, with optimal SiAlON formation occurring in the P4VP precursor containing 6 times the stoichiometric amount of carbon. Increasing the carbon content further suppresses SiAlON formation, possibly due to the build-up of back pressure of CO by-products in the pores of the nanocomposite.     

Introduction of silica into thermo-responsive poly(N-isopropyl acrylamide) hydrogels: A novel approach to improve response rates

The response rates of novel thermo-responsive poly(N-isopropyl acrylamide) (PNIPAM) hybrid hydrogels are compared to those of conventional chemically crosslinked PNIPAM hydrogels. The former materials were obtained by applying the sol-gel technology, in which the inorganic silica particles act as physical crosslinks for the organic polymer chains, leading to a semi-interpenetrating polymer network structure. In situ modulated temperature DSC shows that the introduction of hydrophilic silica improves the thermal response rate of the hybrid hydrogels to a great extent as compared to aqueous PNIPAM solutions and conventional PNIPAM hydrogels. Ex situ gravimetrical measurements also illustrate that the shrinking/swelling rate of the hybrid hydrogels is largely improved. It is assumed that the uniform distribution of the SiO₂ units, as demonstrated by cryo-field emission scanning electron microscopy, causes the silica to act as nano-sized water reservoirs, which reduce the characteristic diffusion length of water in the PNIPAM matrix so that it can be transported faster within the hybrid PNIPAM nano-composite.     

微波在化学反应中的应用

针对微波加热在纳米材料制备、有机化学反应、高分子化学反应以及新型炭(碳)材料的制备和加工,特别是在无机纳米粒子改性、聚合物微球合成中的应用进展进行了综述。     

Flexible bi-continuous mesostructured inorganic/polymer composite membranes

Flexible bi-continuous mesostructured polymer/inorganic composite membranes have been synthesized by undertaking co-assemblies of surfactants and inorganic sol-gel processes inside pores of a preformed porous polymer membrane such as PP porous membrane Celgard^® 2400. The pores are interconnected across the membranes, therefore the continuity of the inorganic mesopores across the membranes is guaranteed in principle. The solvent ethanol used for silica sol is conducive to the synthesis of inorganic materials such as silica within the pores although the PP membrane is hydrophobic. The composite membranes show new properties such as transparency, flexibility, uniform nanosized pores and enhanced permeability.     

A Novel Polymeric Substrate with Dual-Porous Structures for High-Performance Inkjet-Printed Flexible Electronic Devices

Inkjet printing has emerged as a promising low-cost and high-performance method for manufacturing printing-based devices. However, the development of optimized substrates for inkjet printing using novel materials is limited. In this study, a novel polymeric substrate optimized for flexible electronic devices is fabricated using thin-film processing and phase inversion of polyethersulfone (PES). The PES film consists of two layers of pores; the upper layer has nano-sized pores that filter the nanoparticles in the conductive ink and allow for high-density aggregation on the substrate, while the lower layer contains micro-scale pores that quickly absorb and drain the ink solvent. The two porous structures lead to higher conductivity and high-resolution printed patterns by minimizing solvent lateral diffusion. Additionally, the PES printing substrate can undergo high-temperature curing of metal nanoparticles, enabling high-resolution pattern printing with low resistance. The PES substrate is highly transparent and flexible, allowing for the fabrication of various printed electronic patterns and the production of high-performance flexible electronic devices.