Vinyl ether-modified poly(hydrogen silsesquioxanes) as dielectric materials

Vinyl ether-modified poly(hydrogen silsesquioxanes) or PHSQ were prepared via a platinum-catalyzed hydrosilylation reaction of PHSQ with an alkyl vinyl ether (VE) in toluene. The product formed in a near quantitative yield and its composition was characterized by multinuclear magnetic resonance spectroscopy. Multi-detector size exclusion chromatography revealed that relative to the PHSQ starting material, the PHSQ-VEs increased in molecular weight and radius of gyration, and the relationship between intrinsic viscosity and molecular weight suggested a branched structure. Thermal analyses indicated a cure onset around 100 DGC; an onset of thermal decomposition at ca. 230 DGC; and mass loss completed by 550 DGC. Evolved gas analysis from thermogravimetric experiments revealed the initial elimination of the ethylene linkage, followed by cleavage of the carbon-carbon bonds. The materials prepared by pyrolysis at 425 DGC were porous. Nitrogen porosimetry measured an increase in microporosity-from 0.187 to 0.295 cm3 g-1 ( < 5 nm) when the VE content was increased from 10 to 50 wt%. The PHSQ-VEs were spin-coated onto silicon wafers and cured either at 400, 425, or 450 DGC. The dielectric constant of the spin-coated films ranged from 2.3 to 3.0, and the modulus was between 2.2 and 12.9 GPa depending on material composition.