Polymer-based nanocomposite films

Keywords Nanocomposites, polymer nanocomposites, plasmonics, ZnO-based nanocomposite films, nanosized fillers, nanocomposite solar cells, nonvolatile memory devices, magnetic fiuorescent nanocomposites... 

The fascinating properties exhibited by nanoparticles, such as blue shift of the absorption spectrum, size-dependent luminescence, etc., are various manifestations of the so-called quantum confinement effect. These unique properties make ZnO a promising candidate for applications in optical and optoelectronic devices [35-38]. Polymer-based nanocomposites are the subject of considerable research due to the possibility of combining the advantages of both polymers and nanoparticles. There are several applications of polymeric nanocomposites based on their optical, electrical and mechanical properties. Further, nanocrystals dispersed in suitable solid hosts can be stabilized for long periods of time. Polystyrene (PS)— an amorphous, optically clear thermoplastic material, which is flexible in thin-film form—is often chosen as a host matrix because of its ideal properties for investigating optical properties. It is one of the most extensively used plastic materials, e.g., in disposable cutlery, plastic models, CD and DVD cases, and smoke-detector housings. 

In the large field of nanotechnology, polymer-based nanocomposites have become a prominent area of current research and development for biomedical applications.In principle, nanocomposites are an extreme case of composite materials in which interface interactions between the two phases, the matrix and the reinforcement, are maximized. In the literature, the term nanocomposite is used for polymers with sub-micrometre dispersions. In polymer-based nanocomposites, nanometre sized particles of inorganic or organic materials are homogeneously dispersed as separate particles in a polymer matrix. Researchers have tried a variety of processing techniques to obtain dense polymer nanocomposite films. The incorporation of nanostructures into polymers can generally be done in different ways as indicated below ... 

Rhim, J.W. Effect of clay contents on meehanieal and water vapor barrier properties of agar-based nanocomposite films.Carbohydr.Polym., 86, 691-699 (2011). 

MaUakpour S, Madani M. Effect of functionalized Ti02 on mechanicaL thermal and sweUing properties of chitosan-based nanocomposite films. Polym Plast Technol Eng 2015 54(10) 1035-42. 

Figure 27. Effect of starch content on WVP of PVOH-Starch based nanocomposite films (10% clay based on base polymers).

Revzin A, Sirkar K, Pishko M. Glucose, lactate, and pyruvate biosensor arrays based on redox polymer/oxidoreductase nanocomposite thin films deposited on photo-lithographically patterned gold electrodes. Sensors and Actuators B 2002, 81, 359-368. 

As mentioned above, the new method of cryochemical synthesis of polymer nanocomposite films has been developed based on co-deposition of M/ SC and monomer vapors at temperature 80K and subsequent low-temperature solid-state polymerization of monomer matrix ([2] and works cited herein). It has been established that a number of monomers (acrylonitrile, formaldehyde, /i-xylylene and its derivatives) polymerize in solid state in absence of thermal movement of molecules owing to own specific supra-molecular structure. When reaction is initiated by y- or UV-radiation the formation of a polymer matrix occurs even at the temperatures close to temperature of liquid helium [66-69]. 

In solvent casting or solution mixing, CNTs are first dispersed in a suitable solvent and then mixed with a polymer solution to obtain a suspension of nanotubes in the polymer. The mix is then poured into suitable die molds and the solvent is allowed to evaporate to leave behind nanocomposite film. Solution based methods offer advantages of lower viscosities which facilitate uniform mixing and dispersion. Ultrasonication or magnetic stirring is typically used to separate and disperse CNTs uniformly in different solvents or... 

In terms of nanocomposite reinforcement of thermoplastic starch polymers there has been many exciting new developments. Dufresne [62] and Angles [63] highlight work on the use of microcrystalline whiskers of starch and cellulose as reinforcement in thermoplastic starch polymer and synthetic polymer nanocomposites. They find excellent enhancement of properties, probably due to transcrystallisation processes at the matrix/fibre interface. McGlashan [64] examine the use of nanoscale montmorillonite into thermoplastic starch/polyester blends and find excellent improvements in film blowability and tensile properties. Perhaps surprisingly McGlashan [64] also found an improvement in the clarity of the thermoplastic starch based blown films with nanocomposite addition which was attributed to disruption of large crystals. 

Nafion [253], poly(vinyl alcohol) [254], and polyamide-6,6 [255]. A procedure often followed for polymers soluble in tetrahydrofuran (THF) is to add TEOS to a THE solution of the polymer, followed by addition of water (4 moles based on Si) in the form of 0.15 M HCl or 0.1 M NH4OH and allowing the reaction to take place. Films are made by casting on an inert substrate such as Teflon and drying under proper conditions. Nafion composite films are made by impregnating swoDen Nafion films in alcohol solution of TEOS. The micro- or nanocomposite films made by the sol-gel process are expected to have technological opportunities in important arena of gas-liquid separations, heterogeneous catalysis, electronic materials, and ceramic precursors. 

To date, silica has been the focus of the majority of studies on oxide-based nanos-tructured materials. One of the major reasons for this is its easy processability, high chemical inertness and exceptional colloidal stability. Moreover, silica can be processed as a thin film with controllable porosity and optical transparency. All these properties make silica ideal for use in model systems, and it is widely used in many industrial areas ranging from paints and drug delivery to composite materials. Zou et al. have recently published a detailed review on the preparation, characterization, properties, and applications of polymer/silica nanocomposites and the reader is referred to this review for in-depth description of the various synthetic routes [16]. 

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