Polymerization polymer-layered silicate

Rheology of various polymer layered-silicate nanocomposites - intercalated, exfoliated and end-tethered exfoliated (prepared by in-situ polymerization from reactive groups tethered to the silicate surface), have been performed in a conventional melt-state rheometer in both oscillatory and steady shear modes. These experimental studies have provided insight into the relaxation of polymer chains when confined by the layers of inorganic silicates, as well as the role of shear in orienting the layered nanocomposites. 

Polymer-layered silicate nanocoiqposites have been dw recent focus of a great deal of polymeric materials research due to enhancements of thermal, mechanical, and transport properties. In this research, diennoset polymer... 

N. Salem, D.A. Shipp, Polymer-layered silicate nanocomposite prepared though in situ reversible addition-fragmentation chain transfer (RAPT) polymerization. Polymer 36 (2005) 8573-8581. 

In this method, monomers are polymerized in between the layered nanofillers. The nanofillers are allowed to swell in a liquid monomer solution, followed by initiation of the polymerization using a suitable initiator such as heat, radiation, light, catalyst etc. resulting in nanocomposites of a linearly or crosslinked polymer matrix. It is said to be the first method used to synthesize polymer-layered silicate nanocomposites based on polyamide 6, and is still widely employed in several nanocomposite fabrications such as in thermosetting polymer-layered silicate nanocomposites. However, only a few studies have attempted to prepare a biodegradable polymer... 

M. Okamoto, S. Mallapragada, B. Narasimhan, Biodegradable polymer/layered silicate nanocomposites a review. Handbook of Biodegradable Polymeric Materials and Their Applications, American Scientibc Publishers, Valencia, California, Vol. 1, 2005, pp. 1 5. 

Abstract This chapter briefely overviews the polymer-layered silicate nanocomposites, including the structure and properties of the layered silicates and their modifications. It also addresses the developments in synthesizing polyolefin/clay nanocomposites by olefin polymerization under catalysis of clay intercalated precatalysts. It mainly focuses on the synthetic routes, structural characterization, and properties of polyolefin/clay nanocomposites. 

Layered silicates, derived from smectite clays, are commonly used as fillers for polymeric materials for ma ny different applications as their chemistries have been extensively studied [22 ]. Polymer-layered silicate nanocomposites have shown improvements in mechanical, thermal, optical, physicochemical, and barrier properties as well as fire resistance compared to pure polymers or conventional composites (composed of micron-sized particles) [5,12]. 

These materials, unlike the other nanophase materials described in this chapter, are nano-sized in only one dimension and thereby act as nanoplatelets that sandwich polymer chains in composites. Mont-morillonite (MMT) is a well-characterized layered silicate that can be made hydrophobic through either ionic exchange or modification with organic surfactant molecules to aid in dispersion [5,23]. Polymer-layered silicates may be synthesized by exfoliation adsorption, in situ intercalative polymerization, and melt intercalation to yield three general types of polymer/clay nanocomposites. Intercalated structures are characterized as alternating polymer and siHcate layers in an ordered pattern with a periodic space between layers of a few nanometers [13], ExfoHated or delaminated structure occurs when silicate layers are uniformly distributed throughout the polymer matrix. In some cases, the polymer does not intercalate... 

Schartel, B. Fire retardancy based on polymer layered silicate nanocomposites, in M. Okamoto, Ed., Advances in Polymeric Nanocomposite. CMC Publishing, Osaka, Japan, 2004 pp. 242-257. 

Essentially two strategies have been considered to prepare polymerlayered silicate nanocomposites. In the so-called intercalative polymerization, the layered silicate is swollen within the liquid monomer (or a monomer solution) so as the polymer formation can occur in between the intercalated sheets. Polymerization is usually promoted either by heat or an appropriate catalyst. In another technique, the layered silicate is mixed with the polymer matrix in the molten state. Under these conditions and if the layer surfaces are enough compatible with the chosen polymer, the polymer can crawl into the interlayer space and form either an intercalated or an exfoliated nanocomposite. In this melt intercalation technique, no solvent is required. 

Lepoittevin, B., Pantoustier, N., Devalckenaere, M., Alexandre, M., Calberg, C., Jerome, R., Henrist, C., Rulmont, A., Dubois, Ph., 2003, Polymer/layered silicate nanocomposites by combined intercalative polymerization and melt intercalation a masteibatch process. Polymer 2033-2040. 

Solution blending, in situ polymerization, and melt blending are three processing techniques used for preparing polymer-layered silicate nanocomposites. In solution blending, a polymeric solution is prepared and layered silicates are swollen in a cosolvent (water, toluene, chloroform, etc.). By mixing the polymeric and silicate nanolayers solutions. 

Ray S.S., Okamoto M., Polymer/layered silicate nanocomposites a review from preparation to processing , Progressin Polymer Science, 2003 28 1539-1641. Alexandre M., Dubois R, Sun T., Garces J.M., Jerome R., Polyethylene-layered silicate nanocomposites prepared by the polymerization-filling technique synthesis and mechanical properties . Polymer, 2002 43 2123-2132. 

The research around the use of montmorillonite to obtaining nanocomposites polymer-MMT has become even more intense. In a review, Biswas and Ray [45] described several features of polymer-MMT nanocomposite materials. Ray and Okamoto [24] reported various characteristics of polymer-layered silicate nanocomposite materials, some of these materials exhibited distinctive properties like biodegradability. Ahmadi et al. [46] reviewed synthetic routes, properties, and future applications of polymer-layered nanocomposites. Significantly, nanocomposites of PAni and PPY with MMT clay via emulsion polymerization technique [47, 48] were found to act as electrorehological fluids, sometimes denominated smart fluids. In this context, Ballav and Biswas [49, 50] reported high yield oxidative polymerization of thiophene, aniline, pyrrole, and furan by MMT— without extraneous oxidant—vis-a-vis nanocomposites formation of the corresponding polymers with MMT. 

Messersmith, P.B. Giaimelis, E.P. (1993). Polymer-layered silicate nanocomposites in situ intercalative polymerization of e-caprolactone in layered silicates. Chem Mater, 5, 1064-1066. 

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