Nanometer-sized hybrid inorganic-organic

Figure 35.3 Nanometer-sized hybrid inorganic-organic proton-conducting membranes consisting of organic poiymers and inorganic components.

Silica nanoparticles have been widely used as fillers in the manufacture of coatings [103], rubber [104], plastics [105], binders [106], functional fibers [107], etc. In recent years, the preparation of organic-inorganic hybrid materials composed of polymers and functionalized silica nanoparticles has been widely investigated. The combination of organic polymer components with nanometer-sized silica fillers in a single material has extraordinary significance for the development of hybrid materials with unique properties. 

The basic idea behind the development of inorganic-organic hybrid materials is similar If the dimensions of the one or both phases making up the composite material are reduced in size down to the nanometer scale or even the molecular level, a synergetic combination of the properties typical of each of the constituents is still expected. It is rather obvious, however, that the materials properties of such nanocomposites will be different from that of classical composites, since many properties correlate with the phase dimension. Since molecular building blocks are now used for the construction of the material instead of macroscopic pieces of matter, the interface (or interphase) between the constituents will clearly play a different role. 

PC nanocomposites are an emerging class of organic-inorganic hybrids that contain a relatively low wt% of nanometer-sized clay. These were first developed in the late 1980s. The dispersion of the nanometer-sized clay in the polymer matrix significantly improves the mechanical, thermal, barrier properties and flame retardancy of the base polymer. Three main types of nanocomposites can be obtained when clay is dispersed in a polymer matrix. This depends on the nature of the components used, including polymer matrix, clay and organic cation. If the polymer cannot intercalate between the silicate sheets, a microcomposite is obtained. The phase-separated composite that is obtained has the same properties as traditional microcomposites. 

Polymer materials are ubiquitous in our daily life. They often consist of more than one species of polymers and, therefore, can be called multicomponent systems, for example, polymer blends and block copolymers. Because of the repulsive interaction between the constituent polymers, multicomponent polymer materials often show phase separation. Organic-inorganic composites are another class of polymer-based multicomponent materials that have attracted considerable interest from researchers because they often exhibit unexpected properties synergistically derived from the constituents. Nanometer-sized particulate fillers, for example, carbon black (CB) and silica (Si) nanoparticles, are known to form hybrids with organic polymers, which show a significant increase in their static and dynamic moduli, strength, and thermal and electrical conductivities. 

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