Crystal structures, polymers intercalants

The topochemical polymerization of 1,3-diene monomers based on polymer crystal engineering can be used not only for tacticity but also for the other chain structures such as molecular weight [ 102], ladder [84] or sheet [ 103] structures, and also polymer layer structures using intercalation reactions [ 104-107]. Some mechanical and structural properties have already been revealed with well-defined and highly or partly crystalline polymers [ 108-111 ]. A totally solvent-free system for the synthesis of layered polymer crystals was also reported [112]. 

Doping may impose further structural effects that depend on the size and nature of the dopant species. Although there may still not be complete accord on the crystal structure of lithium-doped polyacetylene, it appears that at low doping levels entropic factors are important in inserting a small nonaggregating ion, such as Li", into polyacetylene (PAc), with the dopant occupying sites with minimal strain or disruption of the host lattice. Iodine, on the other hand, in the form of IJ and IJ (and possibly higher polyiodides), produces structures in which anions cluster in columns or sheets to form intercalated layers between polymer chains. ... 

Unlike polymer-clay nanocomposites, in rubber-clay nanocomposites complete exfoliation of clay layers results in disappearance of the diffraction maxima in their XRD patterns. However, this can also occur due to other reasons, like extremely low concentration of clay materials in the composites, crystal defects, etc. The majority of the reports on rubber-clay nanocomposites display the intercalated or swollen nature of the clay structures. The presence of the basal reflections in the XRD patterns of such type of nanocomposites indicates that the clay crystal structure is not destroyed completely. But, shifting of their positions to lower 26 values is interpreted as an expansion of the interlayer region by the macromolecular rubber chains. Besides, broadening of the characteristic reflections in nanocomposites is often related to the defects in the crystal layer stacking caused by the interlayer polymeric species. 

Incorporation of nanofrllers into polymer matrix has been proved to be a powerful tool in order to increase the polymer properties (Lin et al. 201 la, b). It is widely accepted that addition of nanofrller into bio-based matrixes in order to fabricate nano-biocomposite materials could be a powerful solution to improve these properties (Alexandre and Dubois 2000 Bordes et al. 2009 Sinha Ray and Okamoto 2003). Studies on mbular silica-based naturally occurring nanoparticles as reinforcing material is still new (Ismail et al. 2008 Prashantha et al. 2011). Halloysite particles are readily obtainable and are much cheaper than other nanoparticles such as CNTs. More importantly, the unique crystal structure of HNTs resembles that of CNTs, and therefore halloysite particles may have the potential to provide cheap alternatives to expensive CNTs because of their mbular stmcture in nanoscale. Moreover, due to its similarity to other layered clay minerals such as MMT, halloysite has the potential to be further intercalated or exfoliated chemically or physically (Tang et al. 2011). 

This system does not increase the carbon monoxide or soot produced during the combustion, as many commercial FRs do [233]. Other polymer silicate nanocomposites based on a variety of polymers, such as polystyrene, epoxy and polyesters, have been prepared recently by melt intercalation [236]. A direct synthesis of PVA-clay (hectorite) complexes in water solution (hydrothermal crystallization) was reported [237]. It was assumed that the driving force of this phenomenon, at least kinetically, can be described in terms of a simple diffusion reaction of polymers/monomers into clay-layered structures. 

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