Platelet intercalated

Clay is becoming an increasingly popular additive today. It is delivered to the extruder as a powdery material, but at the microscopic (nanometer) level it is comprised of stacked platelets. Clay is employed in so-called nanocomposites, whose name is derived from the fact that the matrix polymer penetrates between the platelets (intercalates). Under proper processing conditions, the platelets maybe separated from one another (exfoliated) for further property enhancement. Mechanical and barrier properties (resistance to gas permeation) may be greatly improved by using clay. 

Of special interest to intercalation studies are complex non-stoichiometric systems, such as the so-called misfit layer chalcogenides that were first synthesized in the 1960s [45]. Typically, the misfit compounds present an asymmetry along the c-axis, evidencing an inclination of the unit cell in this direction, due to lattice mismatch in, say, the -axis therefore these solids prefer to fold and/or adopt a hollow-fiber structure, crystallizing in either platelet form or as hollow whiskers. One of the first studied examples of such a misfit compound has been the kaolinite mineral. 

The pyridine intercalate is blue-black. Examination of the individual platelets under a microscope reveals a characteristic exfoliated appearance. Hexagonal symmetry is retained with a = 3.325 A and c/2 = 12.03 A. Comparison with the slab thickness for the parent 2H(a)-TaS2 shows a c-axis expansion, 8, of 5.99 A. The following d values have been obtained for low-angle X-ray diffraction lines 12.03, 6.015,4.010,3.008, 2.880, and 2.859 A. 2TaS2 C5HsN is also super conducting with a transition temperature of 3.5 0.3°K2,3... 

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. 

Morphology evolution is thus found to be dependent on the processing technique applied to disperse the nanoparticles. The latex-blended and prevulcanized nanocomposites show predominant exfoliation with some intercalation, especially in uncured and prevulcanized samples. In conventionally cured but latex-blended nanocomposites, realignment of NA particles is visible, with a greater tendency of NA platelets towards agglomeration. In solid state mixing, the dispersion is still poorer. XRD studies also corroborate the above observations. 

MePOR species and other complexes in cationic clays can be located at the edges of packed platelets, in the interlamellar space or in the mesopores present (Scheme 10.9). A review of the early data in this area is available.[86] The flat metallo macrocycles under clay synthesis conditions help to induce layer silicate formation, the complexes being intercalated between the layers. Whereas with monooxygen atom donors, alkanes can be oxygenated with significantly enhanced activities compared with the homogeneous case, in every case the expected products (ol/on) were obtained. Competitive oxygenation of adamantane and pentane shows lower... 

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