Polymer nanocomposites synthesis procedures

Ring-opening metathesis polymerization accompanied by fiee-radical addition of cychc alcohols appears to be the optimum procedure for the synthesis of hybrid Si02-polymer nanocomposites exhibiting minimum shrinkage. The synchronous... 

POLYMER NANOCOMPOSITE STRUCTURE AND DISPERSION 12.2.1 Synthesis Procedures... 

Muller and coworkers prepared disc-like polymer Janus particles from assembled films of the triblock copolymer SBM and, after hydrolysis of the ester groups into methacrylic acid units, used these as Pickering stabilizer in the soap-free emulsion polymerization of styrene and butyl acrylate [111]. Armes and coworkers described the synthesis of PMMA/siUca nanocomposite particles in aqueous alcoholic media using silica nanoparticles as stabilizer [112], extending this method to operate in water with a glycerol-modified silica sol [113, 114]. Sacanna showed that methacryloxypropyltrimethoxysilane [115] in the presence of nanosized silica led to spontaneous emulsification in water, which upon a two-step polymerization procedure afforded armored particles with an outer shell of PMMA [116]. Bon and coworkers demonstrated the preparation of armored hybrid polymer latex particles via emulsion polymerization of methyl methacrylate and ethyl methacrylate stabilized by unmodified silica nanoparticles (Ludox TM O) [117]. Performance of an additional conventional seeded emulsion polymerization step provided a straightforward route to more complex multilayered nanocomposite polymer colloids (see Fig. 14). 

Thiol-containing polyphenol was synthesized by peroxidase-catalyzed copolymerization of p-hydroxythiophenol and p-ethylphenol in reverse micelles (254). CdS nanoparticles were attached to the copolymer to give polymer-CdS nanocomposites. By a similar procedure, polyphenol-iron oxide composites were synthesized (242). The reverse micellar system was also effective for the enzymatic synthesis of poly(2-naphthol) showing a fluorescence characteristic of the naphthol chromophore (255). nmr, ir, and uv analyses showed the formation of the polymer with quinonoid structure. 

Several reports related to CdS nanocrystals incorporated in PS matrix have been reported in the literature [200-202]. Zhao et al. described preparation of small nanoparticles of CdS by a hydrothermal procedure in an aqueous solution that yields transparent CdS/PS nanocomposite films [200]. CdS/PS nanocomposites were also prepared successfully using in-situ thermolysis synthesis of a cadmium thiolate precursor dispersed in the polymer [201, 202]. The preparation of CdS/PS via a thermolysis method has several interesting advantages with respect to the common methods of precipitation for example, the CdS precursor is easy to prepare and is stable under normal conditions. The thermal and structural properties of CdS/PS nanocomposites also were broadly investigated [201,202]. 

Kaminsky [92] was the first to report a method in which the filler surfaces were treated with metallocene-based catalyst for the production of filled polyolefins. In this method, at first under inert atmosphere, the clay surface is treated with an alkylaluminum compound to reduce the residual water content. In the second step, the catalyst or cocatalyst solution is impregnated onto the clay surface followed by washing with an anhydrous solvent to avoid excess catalyst leaching from the support during the polymerization. Additional alkylaluminum compounds may be used during the course of polymerization. This polymerization-filling technique is a widely used procedure for the synthesis of polymer/clay nanocomposites using coordination catalysts [60, 93, 94]. 

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