SYNTHESIS, CHARACTERIZATION, AND PLATINUM-CATALYZED HYDROSILYLATION CROSS-LINKING OF UNSATURATED SI-H CARBOSILANES - RANDOM 2/1/1 AND 2/SIMILAR-TO-1/SIMILAR-TO-3 COPOLY(METHYLSILYLENE CIS-1,4-BUT-2-ENYLENE 1,2-BUT-3-ENYLENE AND TRANS-1,4-BUT-2-ENYLENE 1,2-BUT-3-ENYLENE) - PHYSICAL-PROPERTIES OF ALIPHATIC CARBOSILANE THERMOSETS, CARBOSILANE CARBON, AND CARBOSILANE GLASS COMPOSITES

Low molecular weight random copoly(methylsilylene/cis- and trans-1,4-but-2-enylene/1,2-but-3-enylene) (I) in which the ratio of methylsilylene units to cis- and trans-1,4-but-2-enylene units to 1,2-but-3-enylene units is approximately 2:1:1 has been prepared by the reaction of methyldichlorosilane, 1,3-butadiene, and magnesium in THF. Alternatively, random copolymers (II) in which the ratio of these units is approximately 2:approximately 1:approximately 3 can be prepared by a two-step reaction sequence. Copolymers I and II have been characterized by H-1, C-13, and Si-29 NMR as well as FT-IR spectroscopy. Their molecular eight distributions have been determined by gel permeation chromatography (GPC), their thermal stabilities in nitrogen evaluated by thermogravimetric analysis (TGA), and their glass transition temperatures (T(g)) measured by differential scanning calorimetry (DSC). Platinum-catalyzed hydrosilylation cross-linking of I and II yields thermoset materials. The bending modulus (log E'), tan delta and T(g) of these cross-linked materials have been measured by dynamic mechanical thermal analysis (DMTA). Carbon fabric has been treated with a mixture of either copolymer I or II and catalytic amounts of platinum. Multiple layers of coated carbon fabric have been consolidated (cured) to yield aliphatic carbosilane/carbon composite materials. Glass-reinforced composites have been prepared in a similar manner. The interlaminar shear strengths of these materials have been determined by short beam shear. Flexure strengths and moduli of elasticity of these composite samples have been measured. The ultimate compressive strengths and compression moduli as well as the tensile strengths and elastic moduli of these have been determined.