5. In Situ Polymerization 3907 5.1. General Polymerization 3907 5.2. Photopolymerization 3910 5.3. Surface-Initiated Polymerization 3912 5.4. Other Methods 3913 6. Colloidal Nanocomposites 3913 6.1. Sol-Gel Process 3914 6.2. In Situ Polymerization 3916 6.2.1. Emulsion Polymerization 3917 6.2.2. Emulsifier-Free Emulsion Polymerization 3919 6.2.3. Miniemulsion Polymerization 3920 6.2.4. Dispersion Polymerization 3921 6.2.5. Other Polymerization Methods 3923 6.2.6. Conducting Nanocomposites 3924 6.3. Self Assembly 3926 7. Other Preparative Methods 3926 8. Characterization and Properties 3928 8.1. Chemical Structure 3928 8.2. Microstructure and Morphology 3929 8.3. Mechanical Properties 3933 8.3.1. Tensile, Impact, and Flexural Properties 3933 8.3.2. Hardness 3936 8.3.3. Fracture Toughness 3937 8.3.4. Friction and Wear Properties 3937 8.4. Thermal Properties 3938 8.5. Flame-Retardant Properties 3941 8.6. Optical Properties 3942 8.7. Gas Transport Properties 3943 8.8. Rheological Properties 3945 8.9. Electrical Properties 3945 8.10. Other Characterization Techniques 3946 9. Applications 3947 9.1. Coatings 3947 9.2. Proton Exchange Membranes 3948 9.3. Pervaporation Membranes 3948 9.4. Encapsulation of Organic Light-Emitting Devices 3948

Polymer/Silica Nanocomposites: Preparation, Characterization, Properties, and Applications

Up to the end of the nineteenth century, phenol was recovered primarily from coal tar. With the commercialization of the phenolic resins, the demand for phenol grew significantly. Currently, the cumene-to-phenol process is the predominant synthetic route for the production of phenol. It is accompanied by acetone as a co-product. Cumene is oxidized with oxygen to form cumene hydroperoxide. The peroxide is subsequently decomposed to phenol and acetone, using a strong mineral acid as catalyst. The products are purified in a series of distillation columns. The cumene-to-phenol process is described in more detail in this chapter. An overview is given about synthetic routes via direct oxidation of benzene. None of these alternative routes has been commercialized. The chapter also gives an overview of global supply and use of phenol in 2008. Finally, the main natural sources and synthetic routes for cresols, xylenols, resorcinol, and bisphenol-A are described. These components are used as comonomers for special phenolic resins.

Phenolic Resins: A Century of Progress

A novel epoxy system was developed through the in situ curing of bisphenol A type epoxy and 4,4′-diaminodiphenylmethane with the sol–gel reaction of a phosphorus-containing trimethoxysilane (DOPO–GPTMS), which was prepared from the reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with 3-glycidoxypropyltrimethoxysilane (GPTMS). The preparation of DOPO–GPTMS was confirmed with Fourier transform infrared, 1H and 31P NMR, and elemental analysis. The resulting organic–inorganic hybrid epoxy resins exhibited a high glass-transition temperature (167 °C), good thermal stability over 320 °C, and a high limited oxygen index of 28.5. The synergism of phosphorus and silicon on flame retardance was observed. Moreover, the kinetics of the thermal oxidative degradation of the hybrid epoxy resins were studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2354–2367, 2003

Preparation, thermal properties, and flame retardance of epoxy–silica hybrid resins

Cryogenic properties of SiO2/epoxy nanocomposites

Silica aerogels are amorphous materials with remarkable properties, such as very high porosity and specific surface area, and low bulk density and thermal conductivity. However, the potential applications of these materials are limited as they exhibit poor mechanical strength. Nevertheless, silica aerogels allow easy incorporation of different compounds into their structure, enabling the production of materials with distinct characteristics from those of the native silica aerogels. The addition of particles, polymers or fibers, for improving the mechanical, optical or thermal properties has been extensively investigated by several authors in the last decade. A relatively recent alternative is their modification with carbon nanomaterials, which include carbon nanotubes, carbon nanofibers, graphene and carbon aerogels. These nanostructures have well-known characteristics, such as high electrical conductivity and high mechanical strength. The combination of these carbon materials with silica aerogels can lead to new materials with unique electrochemical performance, and thermal and adsorption properties that can be useful in several fields such as electronics, insulation and wastewater treatment. This paper presents a literature review on the synthesis of composite systems containing silica aerogels and carbon nanostructures, and describes their new properties and applications. Examples are the treatment of oily water and removal of heavy metals from wastewater, as well as their application as thermal insulators or anode materials. Along with these new properties, very promising results in mechanical reinforcement were already observed with the inclusion of carbon nanostructures in silica aerogel matrices, but there is still room for further developments in this regard.

Advances in carbon nanostructure–silica aerogel composites: a review

This article describes the preparation of novolac-type phenolic resin/silica hybrid organic-inorganic nanocomposite, with a sol- gel process. The coupling agent was used to improve the interface between the organic and inorganic phases. The effect of the structure of the nanocomposite on its physical and chemical properties is dis- cussed. The coupling agent reacts with the resin to form covalent bonds. The structure of the modified hybrid nanocomposites was identified with a Fourier transform infrared spectroscope. The silica network was characterized by nuclear magnetic resonance imaging ( 29 Si NMR). Results revealed that Q4 (tetrasubstituted) and T3 (trisubstituted) are the dominant microstructures. The size of the silica in the phenolic resin was characterized with a scanning electron microscope. The size of the particles of inorganic silica in the modified system was less than 100 nm. The nanocomposite exhibited good transparency. Moreover, the thermal and mechanical properties exhibited significant improvement. The modified hybrid composite exhibited favorable thermal properties. The temperature at which a weight loss of 5% occurred increased from 281 to 350 °C. The flexural strength increased by 6 -30%. The limiting oxygen index of the nanocom- posite reached 37, and the Underwriters Laboratory test was 94V-0. Consequently, these materials possess excellent flame-retardant properties. © 2003 Wiley Periodicals,

Preparation, characterization, and properties of novolac‐type phenolic/SiO2 hybrid organic–inorganic nanocomposite materials by sol–gel method

Purple sweet potato (PSP) powder with anthocyanins possesses the ability to reduce oxidative stress and inflammation. Studies have presumed a positive correlation between body fat and dry eye disease (DED) in adults. The regulation of oxidative stress and inflammation has been proposed as the mechanism underlying DED. This study developed an animal model of high fat diet (HFD)-induced DED. We added 5% PSP powder to the HFD to evaluate the effects and underlying mechanisms in mitigating HFD-induced DED. A statin drug, atorvastatin, was also added to the diet separately to assess its effect. The HFD altered the structure of lacrimal gland (LG) tissue, reduced LG secretory function, and eliminated the expression of proteins related to DED development, including α-smooth muscle actin and aquaporin-5. Although PSP treatment could not significantly reduce body weight or body fat, it ameliorated the effects of DED by preserving LG secretory function, preventing ocular surface erosion, and preserving LG structure. PSP treatment increased superoxide dismutase levels but reduced hypoxia-inducible factor 1-α levels, indicating that PSP treatment reduced oxidative stress. PSP treatment increased ATP-binding cassette transporter 1 and acetyl-CoA carboxylase 1 levels in LG tissue, signifying that PSP treatment regulated lipid homeostasis maintenance to reduce the effects of DED. In conclusion, PSP treatment ameliorated the effects of HFD-induced DED through the regulation of oxidative stress and lipid homeostasis in the LG.

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Dai-Lin Wu

Papers

Preparation, characterization, and properties of novolac‐type phenolic/SiO2 hybrid organic–inorganic nanocomposite materials by sol–gel method

Purple Sweet Potato Powder Containing Anthocyanin Mitigates High-Fat-Diet-Induced Dry Eye Disease