Polymerization silicate nanocomposites

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. 

Moraes RP, Valera TS, Demarquette NR, et al. (2009) Influence of granulometry and organic treatment of a BrazUian montmorillonite on the properties of poly(styrene-co-n-butyl acrylate)/layered silicate nanocomposites prepared by miniemulsion polymerization. J Appl... 

Several techniques such as intercalation of polymer from solution, in-situ intercalative polymerization, melt intercalation, direct mixture of polymer and particulates, template synthesis, in-situ polymerization and solgel process, are being employed for the preparation of polmer-layered silicate nanocomposites. Among them the most common and important approaches are in-situ polymerization, solution-induced intercalation method, and melt processing method, which are briefly discussed below. 

Bergman, J. S., Chen, H., Giarmelis, E. R, Thomas, M. G., and Coates, G. W. 1999. Synthesis and characterization of polyolefin-silicate nanocomposites A catalyst intercalation and in situ polymerization approach. 

Alexandre, M., Dubois, R, Sun, T., Garces, J. M., and Jerome, R. 2002. Rolyethylene-layered silicate nanocomposites prepared by the polymerization-filling technique S5mthesis and mechanical properties. Polymer 43 2123-2132. 

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. 

It was the pioneering work of Toyota researchers toward the development of polymeric nanocomposites in the early 90s [1, 2], in which electrostahcally held 1-nm-thick layers of the layered aluminosilicates were dispersed in the polyamide matrix on a nanometer level, which led to an exponenhal growth in the research in these layered silicate nanocomposites. These nanocomposites were based on the in-situ synthesis approach in which monomer or monomer solution was used to swell the filler interlayers followed by polymerizahon. Subsequently, GianneUs and CO workers [3, 4] also reported the route of melt intercalation for the synthesis of polymer nanocomposites. 

Bottcher and coworkers were the first to report the preparation of polymer clay nanocomposites by ATRP [20]. ATRP initiator-modified layered silicate was prepared by ion exchange between clay and l,T-(N,N,N-trimethylammonium bromide)undecanyl-2-bromoisobutyrate in-situ ATRP was carried out to grow polymer chains from the clay surface. In-situ ATRP between individual silicate layers leads to the direct synthesis of dispersed silicate nanocomposites. Their kinetics study and molecular weight analysis demonstrated that the polymerization followed the ATRP mechanism. 

X. Huang, W.J. Brittain, Synthesis of a PMMA-layered silicate nanocomposite by suspension polymerization, Polymer Preprints 2000, 41, 521-522. 

An alternative to in situ polymerization involves direct intercalation of macromolecules into layered structures. Silicates are most often used. The insertion of polymer molecules into layered host lattices is of interest from different points of view. First, this insertion process leads to the construction of organic-inorganic polylayered composites. Second, the intercalation physical chemistry by itself and the role intercalation plays in the gain of electronic conductivity are of interest. This becomes important in the construction of reversible electrodes " or when improving the physicomechanical properties of nylon-layered silicate nanocomposites, hybrid epoxide clay composites," and nanomaterials based on hectorite and polyaniline, polythiophene or polypyrrole. ... 

Various methods have been developed in order to prepare pol3uner-layered silicate nanocomposites. These include in situ polymerization, polymer intercalation in... 

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. 

Several authors reported the preparation of PET/ layered silicate nanocomposites. The main procedures used for nanocomposites preparations are melt polymerization, common solvent mixing and in-situ polymerization. In most cases, intercalated nanocomposites were obtained. 

---