Agata Wawrzyńczak

Hydrosilylation on Hydrophobic Material-Supported Platinum Catalysts

Abstract. Catalytic activity of platinum supported on styrene-divinylbenzene copolymerand fluorinated carbons was tested in reactions of hydrosilylation of several olefins and the wayof platinum binding to the support surface as well as platinum oxidation states were determined.Catalysts based on the above hydrophobic materials make it possible to obtain high yields ofdesirable reaction products and in most cases the highest activity was shown by polymer-supportedplatinum catalyst. In addition to hydrophobicity, another factor appeared to influence catalyticactivity, namely the kind of the catalyst precursor. It was established that some amount ofunpolymerized vinyl groups that were present on the polymeric support surface was involved inthe interaction with platinum. XPS spectra enabled to determine that platinum was present onthe catalyst surface in 0 and +2 oxidation states, however Pt 0 clearly predominated.Key words: hydrosilylation, hydrophobic material, platinum catalysts, catalytic activity,polymeric.1. IntroductionHydrosilylation, i.e. the addition of Si-H bondto multiple bonds, is an important reaction fromthe viewpoint of both laboratory and commercialscale applications. It was discovered in 1947 [13]and since then it arouses an unceasing interest ofresearchers that is reflected by thousands ofpapers published on this topic. However, a straightmajority of them was devoted to hydrosilylation

Nanosunscreens: from nanoencapsulated to nanosized cosmetic active forms

Abstract Personal care products often contain nanosized components, such as nanoscopic vesicles. Nanosized metal oxides and nanoencapsulated UV organic filters have brought many attentions and technological advantages to sunscreen cosmetic products. Nanosized metal oxide particles are recently in- and extensively used to broaden the protection spectrum and increase the SPF factor by reflecting, scattering and/or absorbing UV radiation. Modern sunscreens contain mineral filters—insoluble titanium dioxide (TiO2), zinc oxide (ZnO) or ceria (CeO2) and zirconia (ZrO2) nanoparticles. Nanosized metal oxides provide superior UV protection by reflecting physically the light and eliminating the unsightly white residues. The inclusion of nanomaterials in day care products (especially facial cosmetics, i.e., creams) has prompted concern regarding the systemic absorption of these particles. An extensive discussion is presented regarding this issue. Nanoencapsulation of traditional organic UV filters is a more recent technological approach to improving the skin preservation, photostability and UV blocking ability of the free radicals/species. Especially, nanostructured polymers and solid lipid carriers (SLC) are interesting carriers for organic filters in sunscreens. Nanoencapsulation enhances the retention of organic sunscreens in the upper layers of the skin and alters the penetration and release profiles of the active molecule according to the novel design and material of the nanoparticle.