XIE Fucheng ^{1, 2}, CHEN Dou ¹, MO Gaoming ¹, HE Liu ¹, HUANG Qing ¹
(1. Ningbo Institute of Material Technology and Engineering, Engineering Laboratory of Advanced Energy Materials, Ningbo 315201, Zhejiang, China; 2. College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, Zhejiang, China)

Abstract: Polycarbosilane (PCS) is an important precursor of silicon carbide (SiC) fibers and ceramics. As a precursor for preparing SiC fibers and ceramics, it has several deficiencies, such as low ceramic yield, which affect the properties of final products.Cyano-polycarbosilane, a new SiC precursor, was synthesized by using hydrosilylation addition reaction of PCS and acrylonitrile, which is not easy for hydrosilylation generally. During the synthetic process, rhodium-containing catalyst and2-methylpropionitrile were used. The ceramic yield of PCSCN would be significantly increased to over 80%, as compared with that of PCS, especially as the rhodium-containing catalyst was used. The molecular structure of PCSCN was analyzed by using IR and NMR, showing that the hydrosilylation reaction was mainly α-addition. In addition, the degree of hydrosilylation increased with increasing reaction time and reaction temperature at the initial stage, but remained almost unchanged when the time was longer than 5 h or the temperature was higher than 60 ℃. Increasing the content of acrylonitrile would lead to increase in the degree of reaction and thus more cyano groups were introduced in PCSCN, but the magnitude was low.
Key words: acrylonitrile; polycarbosilane; hydrosilylation; ceramic yield