Sol–gel derived organic–inorganic hybrid materials: synthesis,characterizations and applications

Organic/inorganic hybrid materials prepared by the sol–gel approach have rapidly become a fascinating new field of research in materials science. The explosion of activity in this area in the past decade has made tremendous progress in both the fundamental understanding of the sol–gel process and the development and applications of new organic/inorganic hybrid materials. Polymer-inorganic nanocomposite present an interesting approach to improve the separation properties of polymer material because they possess properties of both organic and inorganic such as good permeability, selectivity, mechanical strength, and thermal and chemical stability. Composite material derived by combining the sol–gel approach and organic polymers synthesis of hybrid material were the focus area of review It has also been demonstrated in this review that a more complete understanding of their structure–property behavior can be gained by employing many of the standard tools that are utilized for developing similar structure–property relationships of organic polymers. This review article is introductory in nature and gives introduction to composite materials/nanocomposite, their applications and the methods commonly employed for their synthesis and characterization. A brief literature survey on the polysaccharide templated and polysaccharide/protein dual templated synthesis of silica composite materials is also presented in this review article.     

Recent advances in starch–clay nanocomposites

Biological nanocomposites are a valuable addition to the existing nanocomposite materials and eventually can substitute petroleum-based composite materials in numerous applications due to their inherent advantages such as biodegradability, eco-friendliness, low cost, and easy availability to name a few. Recently, polymer–clay nanocomposites have achieved much more attention due to their enhanced properties such as size dispersion and significant enhancement in physicochemical and mechanical properties in comparison to the pure polymer systems. Among various biopolymers, starch is one of the most abundant natural polymers on the earth and is highly valuable due to its chemical and physical properties. Starch polymer has highly increased potential as an alternative to petroleum-based materials. However, starch cannot be used alone and starch–clay nanocomposite has emerged as a new potential green sustainable material. This article focuses on recent progress in starch-based nanocomposites with particular emphasis on starch–clay nanocomposite preparation, properties, and applications.     

Polymer Nanocomposites in Sensor Applications: A Review on Present Trends and Future Scope

Polymers are crucial constituents of modern electronic devices. They can be used in their pristine, composite or nanocomposite forms for several domestic and industrial applications with innumerable unique possibilities. Polymer nanocomposites have gained wide theoretical interest and numerous practical applications in diverse fields of science and technology as they bestow the materials not only with virtuous processability but also with exceptional functionalities. It is evidenced that the electrical conductance of polymer nanocomposite is governed by the conductive filler networks within the polymer matrix. Hence, insignificant variation in the conductive networks can result in noteworthy variations in the output electric signal of polymer nanocomposite. Exploiting this stimuli-responsive performance of conductive networks to the physical parameters, polymer nanocomposites can be harnessed to fabricate novel sensitive sensors to detect vital physical parameters viz.strain/stress, pressure, temperature, solvent or vapor. Technical and phenomenological studies on polymer nanocomposites are still enduring.Advanced explanations are being sought but the mechanisms governing the formation of several polymer nanocomposites are still topics of debate in the material science community. Their in-depth investigation requires copious scientific work. This review analytically sketches the synthesis, microstructures, physiochemical properties and the underlying mechanisms for stimuli-responsiveness to the physical parameters of the polymer nanocomposites as well as their applications in various sensitive sensors and detectors. Thus, it became evocative for this review to focus on their processing methodologies, physiochemical physiognomies, classification and probable potentials of polymer nanocomposites.This review primarily presents the current literature survey on polymer composites and the gap areas in the study encourages the objective of the present review article. Finally, the status, perspectives and the advantages of specific polymer nanocomposites at present are summarized. The attention of this review is drawn to the present trends, challenges and future scope in this field of study. Finally, the vital concern and future challenge in utilizing the stimulus responsive behavior of polymer nanocomposites to design versatile sensors for real time applications are elaborately discussed.     

Cellulose Nanocomposites

Cellulose is a linear polysaccharide and one of the world's most abundant biopolymers. It is one of the renewable biopolymers being studied to reduce the dependence on non-renewable mineral oil based products. Cellulose can be used in different kinds of composites, including the recent nanocomposites.The production of nanoscale cellulose fibers and their use in polymer composites gained increasing attention due to their interesting properties and potential applications. This review paper is trying to cover studies done to use various forms of cellulose as reinforcement for different polymers, as matrix, as reinforcement and matrix for the same nanocomposite and as a component in polyblend nanocomposites beside other polymers.     

Polymer/carbon-based quantum dot nanocomposite: forthcoming materials for technical application

This endeavor presents state-of-the-art overview on polymer/carbon-based quantum dot nanocomposite. Carbon-based quantum dot (graphene quantum dot, carbon nanodot, and polymer dot) are ～10nm. Carbon-based quantum dot own exciting features such as tunable optoelectronic and photoluminescence properties, high stability, chemical inertness, low cytotoxicity, and biocompatibility owing to quantum confinement and edge effects. Main emphasis of article was to see the combined effect of polymer and carbon-based quantum dot in nanocomposite. Five major categories have been reviewed in this article including conjugated polymer/carbon-based quantum dot nanocomposite, epoxy/carbon-based quantum dot nanocomposite, polystyrene/carbon-based quantum dot nanocomposite, poly(dimethyl siloxane)/carbon-based quantum dot nanocomposite, and block copolymer/carbon-based quantum dot nanocomposite. The review also refers to cutting edge application areas of polymer/carbon-based quantum dot nanocomposite. Conducting polymer/carbon quantum dot nanocomposite has been integrated in energy storage devices, detectors, and electronic devices. These materials are also promising candidates for bulk heterojunction solar cells and light-emitting diodes. Another important use is the identification and removal of toxic metals. Functional materials have also been used for fluorescence imaging of live cells. Modification of carbon-based quantum dot and incorporation in appropriate polymer matrices can be adopted as powerful future tool enabling desired tailored applicability of nanocomposite in advance high performance technical applications.     

Synthesis and characterization of graphene oxide/modified poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) nanocomposite

In this study, the graphene oxide/poly(N-isopropylacrylamide) nanocomposite modified with 2-mercaptoethanol (GO/MPNIPAM) was synthesized in three stages. N-Isopropylacrylamide polymerization was firstly performed in the presence of azobisisobutyronitrile as an initiator, which was discovered by Homer, and 2-mercaptoethanol as a modifier. Then, the graphene oxide/modified polymer nanocomposite was synthesized by the covalent interactions between carboxylic acids of the graphene oxide and hydroxyl groups of the modified polymer during the esterification reaction. The GO/MPNIPAM nanocomposite includes some percentage of the polymer that improves solubility and stability of the GO sheets in physiological applications; due to the interaction between the MPNIPAM and the modified GO polymer, a bridge-like connection is formed between the GO sheets and the process that leads to remove a large number of hydrophilic groups on the GO nanocomposite and therefore, the GO/MPNIPAM is well dissolved in organic solvents. This property is beneficial for anti-cancer drug delivery as well as π–π interactions between the nanocomposite and aromatic drugs. The nanocomposite is not a toxic material for human body at all and has high capacity for drug delivery. Structure and morphology of the nanocomposite were studied by FTIR, SEM, XRD, UV, TGA and Raman analysis. The analysis done by X-ray diffraction pattern confirmed the presence of graphene oxide in nanocomposites and improved crystalline polymer in nanocomposites.     

高分子/单链高分子纳米粒子复合体系中的界面性质

高分子与纳米粒子复合是改善高分子材料性能的有效途径.近20年来关于高分子/纳米粒子复合物的研究引起了学术界广泛的兴趣.然而由于此类体系中的影响因素复杂,虽然学者们在相关材料性能的研究方面取得了重要进展,但是相关理论的发展却相对滞后,其中一个重要原因是实验上表征手段的缺失,导致对体系中纳米粒子与本体高分子链相互作用规律的认识(尤其是两者界面性质的认识)不够.本文总结和阐述了我们近几年利用分子动力学模拟技术研究高分子/单链高分子纳米粒子复合体系的主要结果,并围绕此类复合体系中的界面结构及动力学性质,讨论并总结了纳米粒子对本体高分子链的作用范围及影响规律,指出单链纳米粒子对熔体链的作用范围与纳米粒子的自身尺寸相当,而与熔体高分子链的分子量没有直接的关系.该结论将为纳米复合体系高分子理论的发展提供重要参考.     

Nanofibrillated cellulose: surface modification and potential applications

Interest in nanofibrillated cellulose has been increasing exponentially because of its relatively ease of preparation in high yield, high specific surface area, high strength and stiffness, low weight and biodegradability etc. This bio-based nanomaterial has been used mainly in nanocomposites due to its outstanding reinforcing potential. Solvent casting, melt mixing, in situ polymerization and electrospinning are important techniques for the fabrication of nanofibrillated cellulose-based nanocomposites. Due to hydrophilic character along with inherent tendency to form strong network held through hydrogen-bonding, nanofibrillated cellulose cannot uniformly be dispersed in most non-polar polymer matrices. Therefore, surface modification based on polymer grafting, coupling agents, acetylation and cationic modification was used in order to improve compatibility and homogeneous dispersion within polymer matrices. Nanofibrillated cellulose opens the way towards intense and promising research with expanding area of potential applications, including nanocomposite materials, paper and paperboard additive, biomedical applications and as adsorbent.     

银/聚合物纳米复合材料

银/聚合物纳米复合材料是一种典型的聚合物基复合材料, 其结构和性能依赖于合成方法,因此开发材料的优异性能必须以深入研究纳米材料的先进合成技术为前提。本文综述了纳米银粒子及其与聚合物形成的纳米复合材料的最新合成进展, 重点介绍了基于液相化学还原方法合成纳米银粒子的新方法, 如溶胶-凝胶法、沉淀法、微乳液法和离子液体法, 以及纳米银粒子的分散技术和原位法合成银/聚合物纳米复合材料的新技术, 并介绍了纳米银复合材料的电绝缘性、表面增强拉曼散射性能、抗菌性及其在生物医学等领域中的应用。     

Permeability of polymer/clay nanocomposites: A review

This is a review of the existing studies on the permeability of gas molecules in nanocomposite materials that consist of inorganic platelet-shaped fillers in polymeric matrices. We describe the dominant mechanisms for the transport of small molecules in polymers and polymer nanocomposites, as well as the procedures for the measurement of the permeability and the diffusivity. The emphasis is given on the various models that have been proposed for the prediction of permeability in polymer-clay nanocomposites. The influence of the characteristics of the inorganic particles on the barrier properties of the composite membrane is discussed and tested using the model and the available experimental data. Some aspects on the methods of improving the barrier properties of the nanocomposite are examined and a few applications of these materials as gas barriers are presented.     

Organosilicon polymers for lithographic applications

Organosilicon polymers have found many uses in the electronics industry in the last twenty-five years due to their low dielectric constant and water-repelling properties. These uses include insulators and encapsulating materials for electronic parts. More recently, siloxanes are being incorporated into polyimides for the purpose of increasing the water resistance, improving mechanical properties and preventing atomic oxygen attack of polyimides. Only in the last few years, some uses of organosilicon polymers in lithography have been reported. In this paper, a review of these uses will be presented and the requirements for organosilicon materials in lithography applications will be outlined.     

The radiation degradation of a nanotube-polyimide nanocomposite

The radiation degradation of a nanotube-polyimide nanocomposite was studied. Radiation chemistry was observed that was not present in the unmodified polymer or in the imbedded single-walled carbon nanotubes (SWNTs) themselves. The tensile properties were found to be improved by the addition of SWNTs in the unirradiated materials, and no deterioration in these properties with irradiation was observed. The SWNTs were found to have a detrimental effect on the optical properties however. The transparency of the composite was degraded significantly faster by electron-beam radiation than the neat polymer was. This may make the SWNT/polyimide composites unsuitable for some space applications. Electron Spin Resonance (ESR) measurements determined that the SWNTs interfere with the radical chemistry in the irradiated materials. This could be due to energy dissipation by the SWNT network, preventing the formation of radical species, or alternatively, preferential reaction or termination of radicals by the nanotubes. FT-Raman spectroscopy was found to be a very useful tool for examining SWNTs embedded at low concentrations. It revealed no signs of SWNT degradation up to 10 MGy.     

Chitosan-based membranes preparation and applications: Challenges and opportunities

Chitosan is an abundant natural biopolymer which finds a variety of applications due to its functionalization extending to pharmacology, controlled drug delivery, healing materials, biomedical engineering, food industry, agriculture, catalysis, biosorbents, wastewater treatment, etc. Chitosan can be transformed to distinct derivatives and composites and be modified and grafted for specific use. Many products like flakes, fine powders, beads, membranes, sponges, fibers, and gels can be formed from chitosan. Degradable membranes made of chitosan in conjunction with other materials have increased their scope and include adsorptive membranes for heavy metal and dyes, biomedical applications of chitosan electrospun nanofibers, metal complexation, polymer and modified chitosan-based nanocomposites, cellulose and chitosan composites in wastewater treatment, fuel cells and catalysis. The review has focused on a number of issues related to the said areas. Application of these composite membranes with real industrial effluents should be done with reference to the commercial adsorbents and then their application for removal of aromatics, oils, surfactants, etc. will become practical. The review covers existing gaps and gives future scope for research and innovation.     

Modification of graphene/graphene oxide with polymer brushes using controlled/living radical polymerization

Graphene nanosheets possess a range of extraordinary physical and electrical properties with enormous potential for applications in microelectronics, photonic devices, and nanocomposite materials. However, single graphene platelets tend to undergo agglomeration due to strong π–π and Van der Waals interactions, which significantly compromises the final material properties. One of the strategies to overcome this problem, and to increase graphene compatibility with a receiving polymer host matrix, is to modify graphene (or graphene oxide (GO)) with polymer brushes. The research to date can be grouped into approaches involving grafting‐from and grafting‐to techniques, and further into approaches relying on covalent or noncovalent attachment of polymer chains to the suitably modified graphene/GO. The present Highlight article describes research efforts to date in this area, focusing on the use of controlled/living radical polymerization techniques. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Nanocomposite membranes for organic solvent nanofiltration

Organic solvent nanofiltration (OSN) is a molecular separation method which offers a sustainable and reliable solution compared to the conventional energy-intensive separation processes. OSN can be successfully applied to several applications, such as food, pharmaceutical, petrochemical and fine-chemical industries. Current research on OSN membranes mainly focuses on polymeric materials due to the ease of processing, controlled formation of pores, lower fabrication costs and higher flexibility as compared with inorganic materials. However, there are some limitations for the polymeric membranes which can be partially surmounted by adding nanoscale fillers into the polymeric matrix to make nanocomposite membranes. This review aims to comprehensively evaluate and report the advances in nanocomposite membranes prepared by using either different nanoscale fillers or various fabrication methods for OSN applications. Nanoparticles that will be discussed include metal-organic framework, graphene oxide, carbon nanotubes, silica, titanium, gold, zeolite and other fillers. The incorporation of these nanoscale fillers into the polymeric membranes can positively influence the mechanical strength, chemical and thermal stability, hydrophilicity, solute selectivity and solvent permeance. This study may provide helpful insights to develop next-generation of OSN membranes for years to come.     

Multifunctional hybrids by combining ordered mesoporous materials and macromolecular building blocks

This critical review presents and discusses the recent advances in complex hybrid materials that result from the combination of polymers and mesoporous matrices. Ordered mesoporous materials derived from supramolecular templating present high surface area and tailored pore sizes; pore surfaces can be further modified by organic, organometallic or even biologically active functional groups. This permits the creation of hybrid systems with distinct physical properties or chemical functions located in the framework walls, the pore surface, and the pore interior. Bringing polymeric building blocks into the game opens a new dimension: the possibility to create phase separated regions (functional domains) within the pores that can behave as "reactive pockets" of nanoscale size, with highly controlled chemistry and interactions within restricted volumes. The possibilities of combining "hard" and "soft" building blocks to yield these novel nanocomposite materials with tuneable functional domains ordered in space are potentially infinite. New properties are bound to arise from the synergy of both kinds of components, and their spatial location. The main object of this review is to report on new approaches towards functional polymer-inorganic mesostructured hybrids, as well as to discuss the present challenges in this flourishing research field. Indeed, the powerful concepts resulting from the synergy of sol-gel processing, supramolecular templating and polymer chemistry open new opportunities in the design of advanced functional materials: the tailored production of complex matter displaying spatially-addressed chemistry based on the control of chemical topology. Breakthrough applications are expected in the fields of sustainable energy, environment sensing and remediation, biomaterials, pharmaceutical industry and catalysis, among others (221 references).     

Cellulose nanomaterial reinforced polymer nanocomposites

Several forms of cellulose nanomaterials, notably cellulose nanocrystals and cellulose nanofibrils, exhibit attractive properties and are potentially useful for a large number of industrial applications. These include the paper and cardboard industry, use as reinforcing filler in polymer nanocomposites, basis for low-density foams, additive in adhesives and paints, as well as a wide variety of filtration, electronic, food, hygiene, cosmetic, and medical products. This entry focuses on cellulose materials as filler in polymer nanocomposites. The ensuing mechanical properties obviously depend on the type of nanomaterial used, but the crucial point is the processing technique. The emphasis is on the melt processing of such nanocomposite materials that has not yet been properly resolved and remains a challenge.     

Synthesis of asymmetric inorganic/polymer nanocomposite particles via localized substrate surface modification and miniemulsion polymerization

Asymmetric nanocomposite particle pairs of polystyrene and silica were prepared via one-step miniemulsion polymerization for the first time. The transmission electron microscopy images showed that these nanocomposite particle pairs were monodisperse and highly asymmetric in morphology. The key to obtaining the asymmetric nanocomposite particle pairs was the combination of miniemulsion polymerization and the local surface modification of silica substrates. Because of localized surface modification on the silica surface, the nucleation and formation of the polymer nodule in miniemulsion polymerization took place only in the modified area on the silica surface, thus ensuring the asymmetric morphology. The asymmetrical materials obtained by the facile and effective method will have significant potential applications in some areas including biomedical fields.     

Structure–property relationships of polymer blend/clay nanocomposites: Compatibilized and noncompatibilized polystyrene/propylene/clay

Polymer blends represent an important class of materials in engineering applications. The incorporation of clay nanofiller may provide new opportunities for this type of materials to enhance their applications. This article reports on the effects of clay on the structure and properties of compatibilized and noncompatibilized polymer blends and presents a detailed process for quantitative analysis of the elastic moduli of polymer blend/clay nanocomposites, based on immiscible polystyrene/polypropylene (PS/PP) blends with or without maleated PP as the compatibilizer. The results show that in the noncompatibilized PS/PP/clay nanocomposite clay locates solely in the PS phase, whereas in the compatibilized nanocomposite clay disperses in both phases. The addition of clay to both polymer blends reduces the domain size significantly, modifies the crystallinity and improves the stiffness. The Mori–Tanaka and Christensen's models offer a reasonably good prediction of the elastic moduli of both types of nanocomposites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Application of thermal analysis methods for characterization of polymer/montmorillonite nanocomposites

Thermal analysis is a useful tool for investigating the properties of polymer/clay nanocomposites and mechanisms of improvement of thermal properties. This review work presents examples of applications of differential scanning calorimetry (DSC), modulated temperature differential scanning calorimetry (MT-DSC), dynamic mechanical thermal analysis (DMA), thermal mechanical analysis (TMA), thermogravimeric analysis (TG) and thermoanalytical methods i.e. TG coupled with Fourier transformation infrared spectroscopy (TG-FTIR) and mass spectroscopy (TG-MS) in characterization of nanocomposite materials. Complex behavior of different polymeric matrices upon modification with montmorillonite is briefly discussed.