Preparation of liquid polycarbosilane containing vinyl ether group and its rapid curing through thiol-ene click reaction

In this study, an SiC ceramic precursor vinyl ether–grafted liquid polycarbosilane (VE–LHBPCS) with approximate formulas of [SiH 1.95 (OCH 2 CH 2 OCH = CH 2 ) 0.05 CH 2 ] n was designed and synthesized. In order to cross-link the ceramic precursor via fast thiol-ene click reaction. The VE–LHBPCS was mixed with 1-wt% ultraviolet (UV) decomposable free radical initiator BAPOs and 7-wt% bis-thiol compound 1,6-hexanedithiol. According to Fourier transform infrared spectroscopy spectroscopy and photolithography experiment, more than 80% vinyl ether group was consumed within 3 s, and photolithography pattern with clear boundary could be formed after UV irradiation for only 1 s. Even for the VE–LHBPCS mixture with a thickness of 4 mm, 20-s UV irradiation was sufficient to cure it with smooth surface and regular edge. Thermal gravimetric analysis demonstrated that the UV-cured VE–LHBPCS mixture had a ceramic yield of 70.0 wt% at 1000°C, which was 20 wt% higher than that of raw LHBPCS. After pyrolysis up to 1000°C, about 29.5% isotropic linear shrinkage associated with the precursor-to-ceramic conversion was observed, and black dense ceramic with a density of 2.49 ± 0.09 g/cm 3 and a chemical formula of SiC 1.01 O 0.18 S 0.04 was obtained. With increasing the pyrolysis temperature, the content of element S decreased and the diffraction peaks of β-SiC became sharper and stronger.