Poly(vinyl pyrrolidone-co-octavinyl polyhedral oligomeric silsesquioxane) Hybrid Nanocomposites: Preparation, Thermal Properties, and Tg Improvement Mechanism

A series of poly(vinyl pyrrolidone-co-octavinyl polyhedral oligomeric silsesquioxanes) (PVP-POSS) organic-inorganic hybrid nanocomposites containing different percentages of POSS were prepared via free radical polymerization and characterized by FTIR, high-resolution H-1-NMR, solid-state Si-29-NMR, GPC, DSC, and TGA. POSS contents in these nanocomposites can be effectively controlled by varying the POSS feed ratios which can be accurately quantified by FTIR curve calibration. On the basis Of Si-29-NMR spectra, average numbers of reacted vinyl groups of each octavinyl-POSS macromer are calculated to be 5-7, which depends on POSS feed ratios. Both GPC and DSC results indicate that these nanocomposites display network structure and the degree of crosslinking increases with the increase of the POSS content. The incorporation of POSS into PVP significantly improves their thermal properties (T-g and T-dec) primarily due to crosslinking structure and dipole-dipole interaction between POSS cores and PVP carbonyl groups. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2963-2969, 2009