Efficient curing of polymethylsilane by borazine and reaction mechanism study

An efficient way to improve the low ceramic yield and poor processability of PMS as a SiC precursor utilizing high levels of Is–H, was developed by simply modifying at 70 °C for 1 to ∼3 h in presence of 1 wt.% borazine. The ceramic yield was significantly enhanced from 35 to 87 wt.% and molecular weight increased from 740 to 3554. It is believed that these benefits are due to dehydrocoupling of Si–H of the PMS with N–H of the borazine to form Si–N units, and of Si–H with itself to form Si–(MeSi)Si2 units. The structure evolution of the PMS during treatment was thoroughly studied using TGA, GPC, 29Si CP/MAS-NMR, 1H-NMR, IR and GC-MS. Furthermore, the processability of the PMS was improved controllable by alteration either the content of borazine added or heating time. Green fibers were readily prepared by hand-drawing the improved PMS solution; these were characterized by SEM.