Synthesis and Thermal Stability of Novel Poly(M-Carborane-Siloxanes) with Various Pendant Groups

3rd Annual International Workshop on Materials Science and Engineering

Yang, Xiaoxue^1 ; Zhao, Yanyan^1 ; Wang, Cuicui^1 ; Zhang, Xiaoa^1 ; Jiang, Shengling^1 ; Lyu, Yafei^1

Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing

100029, China^1

关键词: Controlled molecular weight;    Degradation behavior;    Degradation temperatures;    Electronic effects;    Elevated temperature;    Inductive effects;    Spectroscopic technique;    Thermal cyclization;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/250/1/012009/pdf
DOI  :  10.1088/1757-899X/250/1/012009

来源: IOP

【 摘 要 】

Poly(m-carborane-siloxanes) with various pendant groups (P15-P46) were synthesized via polycondensation of m-carborane-containing disilanols (1-4) and highly active bisureidosilanes (5 and 6). The obtained polymers exhibit controlled molecular weight by carefully adjusting the monomer ratio. Standard spectroscopic techniques including FTIR and NMR were utilized to characterize these polymers and satisfactory results were obtained. TGA analysis indicated that the thermal cyclization of polysiloxanes under nitrogen was greatly postponed by the incorporated m-carborane cage, since the siloxane bonds within the main chain were strengthened by the inductive effect of the latter. DSC and FTIR results confirmed that both siloxane unit and carborane cage were oxidized at elevated temperature under air, which contributed to the transformation of the polymers into the mixture of SiO2and B2O3. Therefore, high char yield was obtained. Besides, the electronic effect of pendant groups greatly influenced the degradation behavior of m-carborane-containing polysiloxanes, having nothing to do with their position. The initial degradation temperature (Td5) increases with varying substituent in the order: CH2CH2CF33≈ Ph 2.