高活性磷腈碱催化制备聚二甲基-甲基乙烯基硅氧烷

Preparation of Poly(dimethyl-co-methylvinyl)siloxane by a High Activity Phosphazene Superbase Catalyst

以八甲基环四硅氧烷(D_(4))和四甲基四乙烯基环四硅氧烷(D_(4)^(Vi))为共聚单体、高活性磷腈碱t-BuP4为催化剂进行开环聚合,制得高摩尔质量聚二甲基-甲基乙烯基硅氧烷。研究了催化剂用量、反应温度、反应时间、D_(4)与D^_(4)(Vi)质量比、封端剂用量对反应收率、产物摩尔质量及其分布的影响,并采用红外光谱仪、核磁共振氢谱仪、热重分析仪表征了产物结构和热稳定性。结果表明,随着催化剂用量的增加,共聚反应收率先升后降,共聚产物的数均摩尔质量先升后降,摩尔质量分布系数(PDI)在2.0附近波动;随着反应温度的升高,共聚反应收率提高,共聚产物的摩尔质量升高并趋于稳定,PDI在1.9~2.2之间波动;随着反应时间的延长,共聚反应收率提高并趋于稳定,共聚产物摩尔质量先升后降,PDI在2.0~2.2之间波动;随着单体中D^_(4)(Vi)质量分数的提高,共聚反应收率在80.1%~90.2%之间波动,共聚产物的乙烯基链节摩尔分数实测值比理论值偏低,共聚产物数均摩尔质量降低,PDI在1.7~2.2之间波动;随着封端剂用量的增加,共聚反应收率总体呈下降趋势,共聚产物的数均摩尔质量降低,PDI在1.9~2.3之间波动。综合考虑,较佳的反应参数为催化剂用量5×10^(-6)、反应温度100℃、反应时间30 min、D_(4)与D^_(4)(Vi)质量比95∶5、封端剂用量0.004%,此时共聚反应收率为90.2%,共聚产物数均摩尔质量为3.42×10^(5)g/mol,PDI为2.2;磷腈碱可作为环硅氧烷开环聚合的一类新型高效催化剂使用,进一步提高生产效率。

A high molar mass polydimethyl-methyl vinyl siloxane was prepared by the copolymerization of octamethylcyclotetrasiloxane (D_(4)) and tetramethyl tetravinylcyclotetra siloxane (D^_(4)(Vi)) and high activity phosphazene base t -BuP4 as catalyst for ring-opening polymerization. The effects of catalyst content, temperature, time, mass ratio of D_(4) ∶ D^_(4)(Vi) and the amount of end-capping agent on the yield, the molar mass and its distribution of the copolymers were investigated. FTIR, 1 H NMR and TGA were used to characterize the structure and the thermal properties of the copolymers. The result show that with the increasing catalyst, the yield of the copolymerization first increases and then decreases, the number-average molar mass of the copolymer increases first and then decreases, and the molar mass polydispersity index ( PDI ) fluctuates about 2.0. With the increasing temperature, the yield of the copolymerization increases, the molar mass of the copolymer increases and tends to be stable, and the PDI fluctuates between 1.9 and 2.2;with the prolonged reaction time, the yield of the copolymerization increases and tends to be stable, the molar mass of the copolymer first increases and then decreases, and the PDI fluctuates between 2.0 and 2.2;with the increase of D^_(4)(Vi) mass fraction in the monomer, the copolymerization yield fluctuated between 80.1% and 90.2%, the measured vinyl chain fraction of the copolymer is lower than the theoretical value, the number-average molar mass decreases, and the PDI fluctuates between 1.7 and 2.2. With increasing dosage of end-capping agent, the yield of the copolymer shows a downward trend, the number-average molar mass of the copolymer decreases, and the PDI fluctuates between 1.9 and 2.3. Considering comprehensively, the optimal conditions are as following: catalyst of 5×10^(-6) , temperature of 100 ℃, reaction time of 30 min, mass ratio of D_(4) to D^_(4)(Vi) 95∶ 5, and end-capping agent of 0.004%. Under the conditions, the yield of copolymerization is 90.2%, the number-average molar mass of the copolymer is 3.42×10^(5) , and the PDI is 2.2. The phosphazene base can be used as a new type of efficient catalyst for ring-opening polymerization of cyclosiloxane, which further improves the production efficiency.