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

Keywords: Fragmentation Chain-Transfer ; Self-Assembled Monolayers ; Walled Carbon Nanotubes ; Well-Defined Polymer ; Nitroxide-Mediated Polymerization ; Block-Copolymer Brushes ; Poly(Methyl Methacrylate) Brushes ; Transfer Raft Polymerization ; Quartz-Crystal Microbalance ; Poly(Acrylic Acid) Brushes Reference EPFL-REVIEW-148464doi:10.1021/cr900045aView record in Web of Science Record created on 2010-04-23, modified on 2017-05-10

Polymer Brushes via Surface-Initiated Controlled Radical Polymerization: Synthesis, Characterization, Properties, and Applications

Adv. Mater. 2010, 22, 347–351 2010 WILEY-VCH Verlag Gm The ever worsening energy depletion and global warming issues call for not only urgent development of clean alternative energies and emission control of global warming gases, but also more advanced energy storage and management devices. Supercapacitors, offering transient but extremely high powers, are probably the most important next generation energy storage device. To boost the specific capacitance of supercapacitors, the specific surface area of the electrode materials needs to be as high as possible to promote the electric double-layer capacitances and to accommodate a large amount of superficial electroactive species to participate in faradaic redox reactions. In addition, suitable pore sizes, 2–5 nm, of the porous electrode materials are critical to ease the mass transfer of electrolytes within the pores for fast redox reactions and double-layer charging/discharging. Aerogels are a class of mesoporous materials possessing highly specific surface areas and porosities, from which promising applications in a wide range of areas have been investigated. They are composed of 3D networks of nanoparticles with an average pore size of several nanometers, adjustably falling within the optimal pore sizes of 2–5 nm. Consequently, aerogels are a promising candidate for supercapacitor applications. As to the electrode material, electroactive materials possessing multiple oxidation states/structures that enable rich redox reactions for pseudocapacitance generation are desirable for supercapacitors. Transition metal oxides are such a class of materials that have drawn extensive and intensive research attention in recent years. Among them, RuO2 is themost prominent one with a specific capacitance as high as 1580F g , probably the highest ever reported. The commercialization of RuO2 based supercapacitors, however, is not promising because of the high cost and rareness of Ru. Spinel nickel cobaltite (NiCo2O4) is a low-cost, environmentally friendly transition metal oxide, which has been employed in electrocatalytic water splitting (oxygen evolution) and lithium ion batteries. Its application in supercapacitors, however, received much less attention. Nickel cobaltite has been reported to possess a much better electronic conductivity, at least two orders of magnitude higher, and higher electrochemical activity than those of nickel oxides and cobalt oxides. It is expected to offer richer redox reactions, including contributions from both nickel and cobalt ions, than the two corresponding single component oxides and is a potential cost-effective alternative for RuO2. Based on the above considerations, one would expect nickel cobaltite aerogels, with anticipated good electronic conductivity, low diffusion resistance to protons/cations, easy electrolyte penetration, and high electroactive areas to be a promising candidate for the construction of next-generation, ultrahighperformance supercapacitors. Traditionally, aerogels are prepared with sol–gel processes by taking corresponding alkoxides as the precursors. Alkoxides are generally expensive and sensitive to moisture and heat, requiring careful handling. Recently, to tackle these drawbacks, the epoxide synthetic route, enabling the use of low-cost and stable metal salts as the precursors, was successfully developed to prepare metal oxide aerogels. In this work, we reported the first successful preparation of nickel cobaltite aerogels with the epoxide-driven sol–gel process. The effects of the post-gel-drying calcination temperature on the critical properties of the product aerogels were investigated. At a starting Ni/Co ratio of 0.5 and a post-gel-drying calcination temperature of 200 8C, an optimal combination of composition, crystallinity, specific surface area, pore volume, and pore size was achieved to afford the nickel cobaltite aerogels that showed an extremely high-specific capacitance of 1400 F g 1 under a mass loading of 0.4 mg cm 2 at a sweep rate of 25mV s 1 within a potential window of 0.04 to 0.52V in a 1 M NaOH solution. The excellent reversibility and cycle stability of the product aerogels were also demonstrated. A stoichiometric mixture of nickel and cobalt chlorides was used as the precursor for the preparation of the nickel cobaltite aerogels. After the gel is dried in supercritical carbon dioxide, a post-gel-drying calcination is generally required to acquire preferred composition and/or better crystallinity of the products. The post-gel-drying calcination temperature is thus an important processing parameter to be studied. For referring convenience, we term the product aerogels as Ni–Co–O–T, with Tdenoting the calcination temperature. The T block is omitted for as-prepared samples. Also, for comparison purposes, NiO and Co3O4 aerogels were prepared, termed as Ni–O–T and Co–O–T, respectively. Figure 1a shows the X-ray diffraction (XRD) patterns of the as-prepared product aerogels and those samples calcined at 200 and 300 8C. Surprisingly, nickel cobaltite was formed even at the as-prepared condition. The diffraction peak located at the 2u value

A Cost-Effective Supercapacitor Material of Ultrahigh Specific Capacitances: Spinel Nickel Cobaltite Aerogels from an Epoxide-Driven Sol–Gel Process

http://pubs.acs.org/doi/pdf/10.1021/bm060620d

The future prospects of microbial cellulose in biomedical applications.

CuO nanostructures: Synthesis, characterization, growth mechanisms, fundamental properties, and applications

Synthesis of metal oxide nanostructures by direct sol-gel chemistry in supercritical fluids.

Inorganic−polymer nanocomposites are of significant interest for emerging materials due to their improved properties and unique combination of properties. Methacrylic acid (MA), a functionalization agent that can chemically link TiO2 nanomaterials (n-TiO2) and polymer matrix, was used to modify the surface of n-TiO2 using a Ti−carboxylic coordination bond. Then, the double bond in MA was copolymerized with methyl methacrylate (MMA) to form a n-TiO2−PMMA nanocomposite. The resulting n-TiO2−PMMA nanocomposite materials were characterized by using thermal analysis, electron microscopy, and elemental analysis. The dynamic mechanical properties (Young's and shear modulus) were measured using an ultrasonic pulse technique. The electron microscopy results showed a good distribution of the nanofillers in the polymer matrix. The glass transition temperature, thermal degradation temperature, and dynamic elastic moduli of the nanocomposites were shown to increase with an increase in the weight percentage of nanofibe...

Synthesis of TiO2−PMMA Nanocomposite: Using Methacrylic Acid as a Coupling Agent

Visible light driven TiO 2 photocatalyst nanowire arrays doped with Fe were grown on the surface of functionalized graphene sheets (FGSs) using a sol–gel method in the green solvent, supercritical carbon dioxide (scCO 2 ). The morphology of the synthesized catalysts was studied by SEM and TEM, which showed uniform formation of Fe doped TiO 2 nanowires on the surface of the graphene sheets, which acted as a template for nanowire growth through surface –COOH functionalities. Increasing Fe content in the nanowires gave only small changes in morphology but significantly higher BET surface areas. Optical properties of the synthesized composites were examined by UV and PL spectroscopy which showed a significant reduction in band gap with increasing Fe content, i.e. decreasing from 3.2 to 2.3 eV at 0.6% Fe. High resolution XPS and Raman analysis showed the interaction of Fe with the TiO 2 lattice and also bonding of TiO 2 with –COOH groups on the surface of the graphene sheets. The photocatalytic properties of the prepared catalysts were evaluated under visible light solar irradiation for the photodegradation of 17β-estradiol (E2), an endocrine disrupting hormone which is commonly released into aquatic environments. All prepared catalysts with different ratios of Fe were active in the visible region of the solar spectrum with the photocatalytic activity significantly enhanced with increasing Fe doping levels with a plateau at 0.6–0.8% Fe. The prepared catalysts showed higher activity than both Fe doped TiO 2 and TiO 2 /FGSs composites.

Visible light active Fe doped TiO2 nanowires grown on graphene using supercritical CO2

Grafting from polymerization was used to synthesize nano-titania/polyurethane (nTiO(2)/polyurethane) composite coatings, where nTiO(2) was chemically attached to the backbone of the polyurethane polymer matrix with a bifunctional monomer, 2,2-bis(hydroxymethyl) propionic acid (DMPA). This bifunctional monomer can coordinate to nTiO(2) through an available -COOH group, with two available hydroxyl groups that can react with diisocyanate terminated pre-polyurethane through step-growth polymerization. The coordination reaction was monitored by FTIR and TGA, with the coordination reaction found to follow first order kinetics. After step-growth polymerization, the polyurethane nanocomposites were found to be stable on standing with excellent distribution of Ti in the polymer matrix without any significant agglomeration compared to simple physical mixtures of nTiO(2) in the polyurethane coatings. The functionalized nTiO(2)-polyurethane composite coatings showed excellent antibacterial activity against gram-negative bacteria Escherichia coli; 99% of E. coli were killed within less than one hour under solar irradiation. Self-cleaning was also demonstrated using stearic acid as a model for 'dirt'.

https://iopscience.iop.org/article/10.1088/0957-4484/23/42/425606/pdf

Nano-TiO2/polyurethane composites for antibacterial and self-cleaning coatings

Photodegradation of the natural steroid 17β-estradiol (E2), an endocrine disrupting hormone which is commonly released into aquatic environments, was investigated under simulated sunlight (290–700 nm) using a solar simulator in the presence of several natural water constituents including NO3−, Fe3+, HCO3−, humic acid and turbidity. The E2 degradation followed pseudo-first-order kinetics, with the rate constant decreasing slightly with increasing initial constituent concentration while increasing with the square root of solar intensity in the region of 25–100 mW cm−2. The rate of mineralization based on the total organic carbon (TOC) reduction was always lower than E2 degradation, although the TOC of the solution decreased steadily with irradiation time. In the presence of NO3−, Fe3+, and humic acid, the photodegradation rate increased significantly, attributed to photosensitization by the reactive species, while HCO3− slowed down the degradation rate because of OH scavenging. Turbidity also reduced the photodegradation of E2 by decreasing light transmittance due to attenuation. The solution pH also had a considerable effect on the rate with maximum degradation occurring around a neutral pH of 7.

Paul A. Charpentier

Papers

Synthesis of metal oxide nanostructures by direct sol-gel chemistry in supercritical fluids.

Synthesis of TiO2−PMMA Nanocomposite: Using Methacrylic Acid as a Coupling Agent

Visible light active Fe doped TiO2 nanowires grown on graphene using supercritical CO2

Nano-TiO2/polyurethane composites for antibacterial and self-cleaning coatings

Photodegradation of 17β-estradiol in aquatic solution under solar irradiation: Kinetics and influencing water parameters