Hybrid materials dispersion

Clays have long been used as fillers in polymer systems because of low cost and the improved mechanical properties of the resulting polymer composites. If all other parameters are equal, the efficiency of a filler to improve the physical and mechanical properties of a polymer system is sensitive to its degree of dispersion in the polymer matrix (Krishnamoorti et ah, 1996). In the early 1990s, Toyota researchers (Okada et ah, 1990) discovered that treatment of montmorillonite (MMT) with amino acids allowed dispersion of the individual 1 nm thick silicate layers of the clay scale in polyamide on a molecular. Their hybrid material showed major improvements in physical and mechanical properties even at very low clay content (1.6 vol %). Since then, many researchers have performed investigations in the new field of polymer nano-composites. This has lead to further developments in the range of materials and synthesizing methods available. 

In the specific case of silica nanoparticles-pH EMA hybrid materials, the synthesis relies on obtaining a fine dispersion of silica nanoparticles (with a mean diameter of 7nm) in HEMA monomers (liquid phase). When a homogeneous solution is obtained, a free radical initiator is added at a concentration based on the weight of the monomer mixture. After the initiator dissolution, the solution can be poured into molds or between two glass plates to obtain monoliths or uniform films, respectively, after being cured at temperatures around 60-85 °C for several hours. 

Tong, X., et ah, Enhanced catalytic activity for methanol electro-oxidation of uniformly dispersed nickel oxide nanoparticles - carbon nanotube hybrid materials. Small, 2012. 

Liu etal. [32] reported the characteristics and reactivity of highly ordered mesoporous carbon-titania hybrid materials synthesized via organic-inorganic-amphiphilic coassembly followed by in situ crystallization. In the degradation of Rhodamine B these materials also show enhanced properties due to the dispersion/stabilization of small titania nanocrystals and the adsorptive capacity of the nanocarbon. 

There are thus multiple effects by which the properties of the nanocarbon-semiconductor hybrid material can be different from the simple physical mixture of the two components [1] The nanocarbon offers an effective way for an efficient dispersion of the semiconductor, thus preventing agglomeration, but also providing a hierarchical structure [15] for efficient light harvesting and eventually easy access from gas/liquid phase components (in photocatalytic reactions) or electrolyte (in DSSC). 

Furthermore, the catalytic properties of these hybrid materials strongly depend on the dispersion of the catalytic sites and on the chemical nature of their environment [11,12],... 

The hybrid materials having silica content below 50 wt% were composed of polyimide matrix with finely dispersed silica particles, and their hardness values were very close to that of the matrix polyimide. On the other hand, the hybrid materials having a silica content over 50 wt% were very hard and tough, and their hardness values increased with increasing silica content. In the latter hybrid materials, the silica formed a continuous phase with polyimide as the minor phase that probably acts as binder. This is a new type of polyimide-based composite, and may be referred to as polyimide-reinforced silica glass , al-... 

The methods described above correspond to those attainable with conventional sol-gel chemistry. This strategy is simple, low cost, and yields amorphous hybrid materials, which can contain specific organic molecules, biocomponents or polyfunctional cross-linkable polymers (e.g., telechelic polymers). These materials exhibit an infinity of microstructures, can be transparent, and easily shaped as films or bulks (Fig. 2, Route A). However, they are generally poly-disperse in size and locally heterogenous in chemical composition. 

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