Polymer nanocomposites containing superstructures of self-organized platinum colloids

Colloidal platinum (diameter 1-2 nm) in styrene was prepared in situ by red uction of a platinum(II) compound followed by partial evaporation of styren e, The resulting dispersions were purified from the reaction side-products, and ammonium O,O ' -dialk-yldithiophosphates of different chain length or octadecanethiol was added. Polymerization was started with a radical initia tor. Several parameters were varied and, particularly in the presence of lo ng-chain dialkyldithiophosphates, self-assembled superstructures of metal c olloids appeared at certain conditions in the resulting poly(styrene)-plati num nanocomposites. Unusual hollow shell structures of typical diameters of 50-300 nm were found, which phenomenologically resembled bilayer vesicles in aqueous solutions, although the formation mechanism of the bilayers and the superstructures in the nanocomposites is considered to differ. It is su pposed that the formation of the superstructures in the nanocomposites is i nduced by crystallization of alkyl chains adsorbed at the platinum surface below monolayer coverage.