Polymer clay nanoparticles applications

Examples of the use of nanostructured materials for packaging applications have been given in Chaudhry et al. (2008) and references therein. One of the first market entries into the food packaging arena was polymer composites containing clay nanoparticles (montmorillonite). The natural nanolayer structure of the clay particles impart improved barrier properties to the clay-polymer composite material. Some of the polymers which have been used in these composites for production of packaging bottles and films include polyamides, polyethylene vinyl acetate, epoxy resins, nylons, and polyethylene terephthalate. 

Besides clay-based nanocomposites, there has been huge discussion on the metallic and semiconductor-based hybrid materials. The ability of polymer materials to assemble into nanostructures describes the use of polymers providing exquisite order to nanoparticles. Finally, a discussion on potential applications of polymer—nanoparticle composites with a special focus on the use of dendrite polymers and nanoparticles for catalysis should follow (Polymer-Nanoparticle Composites Part 1 (Nanotechnology), 2010) (Figure 1.15). 

Soft nanohybrid materials with novel organic-inorganic network structures, such as nanohydrogels, soft nanocomposites (solid), and their derivatives are described in the chapter Soft Nanohybrid Materials Consisting of Polymer-Clay Networks. Synthesis of polymer hybrids based on metal-oxide nanoparticles are discussed in Fabrication of Metal Oxide-Polymer Hybrid Nanocomposites. Some properties and applications of these hybrid nanocomposites are also discussed in this chapter. 

Nowadays, ordered inorganic/organic PNs with a finely tuned structure have displaced a lot of traditional composite materials in a variety of applications because the intimate interactions between components can provide enhancement of the bulk polymer properties (i.e., mechanical and barrier properties, thermal stabihty, flame retardancy, and abrasion resistance). The reinforcing nanoparticle/ polymer adhesion is of primarily importance, as it tunes the final properties of the nanocomposite. Polymer/clay nanocomposites (PCNs) meet this demand due to the platelet-type dispersion of the clay filler in the organic matrix [1]. 

With both thermoset and thermoplastic in situ polymerization techniques, there are some fundamentals of polymer nanocomposite synthesis that are weU understood. One fundamental to consider is the interface between polymer and nanoparticle in the final application without a well-designed interface between nanoparticle and polymer, no synthetic technique will yield a good polymer nanocomposite. For in situ polymerization, the focus is on clay nanocomposites, as this field has a wealth of information on structure-property relationships between clay and polymer. Some factors that must be considered include ... 

As already mentioned, PVA is a water soluble polymer used in applications such as packaging films where water solubility is desired. It is the most readily biodegradable of the vinyl polymers, which makes it a potentially useful material in biomedical, agricultural, and water treatment areas, for example, as a flocculant, or scavenger of metal ions. Moreover, due to its water solubility, PVA can also be used as a model for particle dispersion in aqueous suspensions, especially those from CNWs and some clays. As a consequence, PVA has been largely used to produce nanocomposites with clays, cellulose, and chitin whiskers, silver nanoparticles, graphite oxide, and carbon nanotubes. 

In polymer-clay nanocomposites, to truly reach the ultimate in property improvements requires full exfoliation. A fully exfoliate composite yields the maximum interfacial interaction between the nanoparticle and polymer matrix. In order to produce optimally exfoliated systems requires that direct methods be available to measure the level of exfoliation. The ideal analytical method should be rapid, nondestructive, applicable to many sample matrices, low cost, and should require minimal sample preparation. The only method that fits these criteria is wide-angle X-ray diffraction (WAXD). This method, however, has some major drawbacks that will be discussed in detail in this chapter. 

Since nanoparticles in PNC are orders of magnitude smaller than conventional reinforcements, the models developed for composites are not applicable to nanocomposites. However, development of a universal model for PNC is challenging since the shape, size, and dispersion of the nanoparticles vary widely from one system to another. On the one hand, exfoliated clay provides vast surface areas of solid particles (ca. 800 m /g) with a large aspect ratio that adsorb and solidify a substantial amount of the matrix polymer, but on the other hand, the mesoscale intercalated clay stacks have a much smaller specific surface area and small aspect ratio. However, in both these cases the particle-particle and particle-matrix interactions are much more important than in conventional composites, affecting the rheological and mechanical behavior. Thus, the PNC models must include the thermodynamic interactions, often neglected for standard composites. 

Thermoset polymers like polyimide, crosslinked sulfonated poly(ether ether ketone) and polyacrylate can be used for membrane applications. The presence of nanoparticle nucleates the nanopore formation with the assistance of an agent. The nanopore is responsible for the solvent separation and transportation. Membranes such as solvent filters, filters for bacteria and virus, and membrane for gas separation can be developed using clay-polymer nanocomposites [118-119]. 

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