Synthesis of New Functional Silicon-Based Condensation Polymers

Abstract

A new class of photosensitive aromatic polymers containing disilane units was successfully synthesized from new disilane-based monomers such as 1,2-bis(diethylamino)tetramethyldisilane and 1,2-bis(p-aminophenyl)tetrarnethyldisilane. The disilane-contain-ing aramids and polyimides had glass transition temperatures above 190°C, and all the polymers were thermally stable up to 300°C in air. The polymers were photosensitive; their molecular weight decreased rapidly upon ultraviolet light irradiation. The photosensitive polymers, especially the soluble polyimides having diphenyl sulfone units, were potential candidates for positive working photoresist materials. New highly branched polysiloxane star-burst polymers were synthesized by a siloxane synthetic reaction starting from tris[(phenyldimethylsiloxy)dimethylsiloxy]methylsilane and bis[(phenyldimethylsiloxy)methylsiloxy]dimethylsilanol as the initial core (G0-Ph) and the building block, respectively. Thus, the first generation polymer G1-Ph, second generation polymer G2-Ph, and third generation polymer G3-Ph had 6, 12, and 24 phenylsilyl groups in their exterior layers. The formation of the siloxane-based starburst polymers were confirmed by means of ¹H-, ¹³C-, and ²⁹Si-NMR spectroscopy. These polysiloxane starburst polymers were suggested to have spherical structure. Some functionalized starburst polymers were further synthesized by the introduction of functional groups in their exterior layers. New silica-polyimide hybrid materials were prepared by the sol-gel process through the hydrolysis-condensation reactions of tetraethoxysilane in the presence of the polyamic acid (polyimide precursor) in dimethylacetamide, followed by heating at 270°C. The hybrid system having silica content up to 70 wt% had good quality films. The spherical silica particles were dispersed homogeneously in the polyimide matrix. With increasing silica content, the glass transition temperature and decomposition temperature, as well as the modulus of the hybrid films, increased, while the coefficient of thermal expansion decreased.