The Study Of Structure And Performance Of Polycarbosilane Fractions

In this paper, polycarbosilane (PCS) of different molecular weight and narrow molecular weight distribution was gained. It was founded that the structure and the performance in curing and pyrolysis process of PCS fractions are different. This is useful to prepare PCS according to the purpose.Fractional precipitation and GPC column were used to obtain PCS fractions, and PCS fractions of narrow molecular weight distribution and largely different molecular weight were gained using GPC column. The Mark-Houwink constant K andαof PCS at 25℃in THF were calculated: K= 0.00053,α= 0.881 and the calibration curve was also gained.IR of PCS and the carbon and silicon content in PCSs were measured and the curves of infrared-absorbance vs. number of main bonds in PCS were established, including bond between carbon and silicon, bond between methyl and silicon, bond between hydrogen and silicon. Then more detailed structure formula of PCS were gained, and a way showing molecular weight distribution was proposed, that was PCS molecular weight M is described as high (M>30000), middle ( 2500