where Cy ) c-C 6 H 11 ) and two POSS-siloxane copolymers [Cy 8 Si 8 O 11 -(OSiMe 2 ) n O-] (n ) 1, oligomer average 5.4) has been studied in argon, nitrogen, and under vacuum from 30 to 1000 °C. Product gases were analyzed by TGA-FTIR and mass spectroscopy. Analysis of the chars was conducted using cross-polarized (CP) and magic angle spinning (MAS) NMR spectroscopy, X-ray diffraction, density measurements, and gas adsorption analysis. All of the POSS macromers showed a propensity toward sublimation, while the POSS-siloxane copolymers underwent a complex depolymerization-decomposition process. For the copolymer [Cy 8 Si 8 O 11 -(OSiMe 2 ) 5.4 O-] this process included the evolution of cyclic dimethylsiloxanes at 400 °C, cyclohexyl hydrocarbons from 450 to 550 °C, and H 2 liberation from 700 to 1000 °C. Loss of the silsesquioxane "cage" structure occurred upon heating from 450-650 °C and after the evolution of most of the pyrolysis gases. Changes in both char porosity and density accompanied the structural rearrangements. The activation energies for pyrolysis under argon or nitrogen was 56 ( 9 kcal/mol and for oxidation in air was 20 ( 4 kcal/mol.

A series of polyhedral oligomeric silsesquioxanes (POSS) monomers bearing silane or α‐olefin substituents have been prepared and their chemistry explored. Both the POSS silanes and α‐olefin monomers readily participate in hydrosilation chemistry and have been used as starting materials for the preparation of POSS sol–gel‐type reagents. Similarly, POSS silanes and α‐olefins are reactive towards silane‐ and olefin‐functionalized polymers, which makes them useful as grafting reagents. The utility of these reagents as graftable monomers was demonstrated by synthesis of a series of POSS–siloxane–POSS triblock polymers. Thermal­and X‐ray diffraction (XRD) characterization of the triblock polymers was performed in order to examine how the length of the siloxane segment affects the properties of the polymer. The POSS α‐olefin monomers were found to­be unreactive with respect to Ziegler–Natta polymerization. The reaction of POSS α‐olefins with m‐chloroperbenzoic acid (MCPBA) to give POSS epoxides was demonstrated and the thermal stability of the POSS epoxides determined. Copyright © 1999 John Wiley & Sons, Ltd.

The study of organic/inorganic hybrid materials has become an increasingly widespread research focus. The advantage derived from such materials is the combining of two very different compounds which may result in something that bridges the performance gap between the two systems. We have previously reported such hybrid systems prepared by incorporating polyhedral oligosilsesquioxanes (POSS™) into traditional organic polymers by the copolymerization of POSS™ monomers and organic monomers. This presentation will discuss a more convenient method of incorporating POSS™ into a polymer: the blending of POSS™ into organic polymers. The research discussion will focus on the development of the POSS™ macromers used in our studies as well as the POSS™ polymer blends synthesized. One important property enhancement observed is the increase in surface hardness for a POSS™/poly styrene sample.

A series of Polyhedral Oligomeric Silsesquioxane (POSS) monomers bearing reactive hydroxyl functionalities, suitable for incorporation into step-growth polymers, is described. These monomers are difunctional in nature and are particularly well suited for use as chain extenders in the synthesis of polyurethanes. This work describes the synthesis of these POSS monomers and their incorporation into a series of polyurethanes. Preliminary thermal, mechanical and rheological data for the POSS containing polyurethanes will also be discussed.

We have recently begun investigating the rheological behavior of blends containing thermotropic liquid crystalline polymers (LCPs) and isotropic polymers. To aid us in our studies, we have designed a unique instrument for simultaneous visualization of morphology evolution and rheological measurements. Rectilinear shear is used, with a top glass bar being translated relative to a fixed bottom glass bar. The sample is heated by conduction from mica heaters embedded in the substrate materials supporting the bounding glass bars. Shear forces are obtained by measuring the (small) deflection of the bottom glass bar and heating assembly which is designed to be slightly compliant in the flow direction while rigid in direction normal to the sample.