Nanocomposites inorganic phase

Table 3 Freshly synthesized Ti(Ti02)/PPX nanocomposites inorganic phase content...

Composites made with carbon nanostructures have demonstrated their high performance as biomaterials, basically applied in the field of tissue regeneration with excellent results. For example, P.R. Supronowicz et al. demonstrated that nanocomposites fabricated with polylactic acid and CNTs can be used to expose cells to electrical stimulation, thus promoting osteoblast functions that are responsible for the chemical composition of the organic and inorganic phases of bone [277]. MacDonald et al. prepared composites containing a collagen matrix CNTs and found that CNTs do not affect the cell viability or cell proliferation [278]. 

We have presented several examples of the successful preparation of rubber nanocomposites with layered silicate as the inorganic phase. This review explores the idea that the designing and compounding are key factors in obtaining the... 

TEM analysis of the nanocomposite with an A1 content beyond the percolation threshold reveals spherical pure metal nanoparticles with a mean diameter of about 10 nm (Fig. 6a), while below the percolation threshold the composite contains agglomerates of rhombohedral AI2O3 (corundum) with a mean size of 55 nm (Fig. 6c). A sample with a metal content just at the percolation threshold contains metal nanoparticles of 10nm and alumina aggregates of 28 nm in diameter (Fig. 6b). The inorganic phase is homogeneously dispersed within the polymeric matrix in all of the investigated samples. It has been shown that the nanocomposite structure determines the oxidation behaviour of A1 nanoparticles within the polymeric matrix under air exposure. 

Fig. 6 TEM images of Al(Al203)/PPX nanocomposites with different contents of the inorganic phase a sample 5 (12 vol%) b sample 6 (10 vol%), c sample 7 (8 vol%)...

A series of samples of nanocomposites of Ti and PPX with different Ti content has been synthesized (Table 3). AFM analysis shows that the inorganic phase comprises nanoparticles of 10-20 nm in diameter, which are homogeneously distributed between the polymer globules (Fig. 8). 

Thin-film metal (metal oxide)/polymer nanocomposites with different inorganic phase contents were obtained by using the cold-wall vacuum co-deposition technique. A range of metals was shown to be applicable to form nanocomposite thin films with PPX, i.e., Al, Ti, Pd, and Sn. AFM studies show the metal nanoparticles to have a size of 7-50 nm. Within the composite the polymer forms more or less spherical globules with a maximum size of about 200 nm. The interfacial regions between neighbouring polymeric spherulites contain nanoparticles of the inorganic filler. 

The introduction of ferroelectric nanoparticles in polymeric matrices seems attractive for improving the dielectric permittivity of polymeric-based materials. New pyro-and piezoelectric systems have been proposed, and better efficiency has been obtained by using ferroelectric particles with d 700 nm. However, the understanding of correlations between structure and macroscopic properties needs to be improved. Nevertheless, it is interesting to note that smart hybrid materials have been prepared by combining organic and inorganic phases, which illustrates the versatility of such nanocomposites. 

The mercaptide thermolysis may behave differently in the presence or absence of polymers [Conte et al., 2007]. However, in most cases, the inorganic phase generated by the thermal degradation of mercaptide molecules dissolved in polymer corresponds exactly to that resulting from the thermal degradation of pure mercaptide. Consequently, a preliminary study of neat mercaptide thermolysis by thermal analysis approaches [differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA)] is usually performed before nanocomposite preparation and characterization. 

Commonly the term "hybrids" is more often used if the inorganic units are formed in situ by the sol-gel process ( Kickelbick, 2007).Meanwhile, use of the word "nanocomposites" implies that materials consist of various phases with different compositions, and at least one constituent phase (for polymer/silica nanocomposites, that phase is generally silica) has one dimension less than 100 nm. A gradual transition is implied by the fact that there is no clear borderline between "hybrids" and "nanocomp)osites"( Kickelbick, 2007). 

When a polymer is present in the reaetion environment, organic-inorganic hybrids are formed spherieal or quasi-spherical siliea partieles are obtained, with dimensions from few nanometres to submicron dimension, carrying out the so-called bottom-up preparation of nanofillers. Nanocomposites are thus formed with an intimate mixture of organic and inorganic phases. 

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