Preparation and characterization of polysiloxane networks containing metallic platinum particles

摘要

Polysiloxane networks obtained via cross-linking of D-4/V-4 polysiloxane served as matrices for incorporation of metallic Pt particles. D-4/V-4 polymer used in the crosslinking was synthesized by equilibrium cationic ring-opening polymerization of the corresponding cyclotetrasiloxane monomers. Linear (H MM H) or cyclic (D-4(H)) hydrosiloxanes, at different hydrosiloxane to D-4/V-4 molar ratios, were applied as crosslinking agents. Platinum species were introduced into the crosslinked products from PtCl4 solution in THF or in isopropyl alcohol via the reduction of Pt4+ to Pt-0 in the presence of active Si-H sites. Various analytical techniques: UV-vis and FTIR spectroscopy, swelling measurements, XRD, SEM, and thermogravimetric analysis were applied to control the progress of the reaction or to characterize the intermediate or final products. IR spectroscopy allowed to determine the efficiency of crosslinking process and to investigate the consumption of un-reacted Si-H groups accompanying the reduction of platinum ions. XRD studies confirmed the incorporation of metallic platinum into all systems. Good thermal stability of obtained products was found using thermogravimetric analysis. According to SEM investigations, the applied network as well as the solvent used in the reduction process influenced the dispersion of metallic particles on the surface of the matrices. The obtained Pt-systems exhibited mainly redox activity in catalytic isopropyl alcohol conversion used as a test reaction. Significant differences in catalytic properties between systems containing different matrices were observed. The promoting effect on the catalytic activity was found in the case of C-P type support, i.e. the polysiloxane network obtained using the cyclic hydrosiloxane as the crosslinking agent. (C) 2015 Wiley Periodicals, Inc.