顺式2,4,6-三甲基-2,4,6-三苯基环三硅氧烷阴离子聚合流变学及立构选择性  

Rheological Characteristics of Cis-2,4,6-Trimethyl-2,4,6- Triphenylcyclotri-Siloxane (Cis-P_3) Polymerization and Its Stereo Control

作　　者：梁培亮 郑震 陈亮 王新灵[1] Peiliang Liang;Zheng Zheng;Liang Chen;Xinling Wang(School of Chemistry and Chemical Technology, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China)

机构地区：[1]上海交通大学化学化工学院金属基复合材料国家重点实验室,上海200240

出　　处：《高分子材料科学与工程》2019年第2期7-13,共7页Polymer Materials Science & Engineering

摘　　要：以四甲基氢氧化铵为引发剂,顺式2, 4, 6-三甲基-2, 4, 6-三苯基环三硅氧烷(Cis-P_3)为单体,通过开环聚合制备了不同规整度的聚甲基苯基硅氧烷。通过在线流变研究发现,Cis-P_3开环聚合体系的存储模量(G’)出现了先下降后上升特征的流变现象。对P_4开环聚合和不同溶剂中Cis-P_3开环聚合的在线流变研究也发现了相同特征的流变现象,且特征流变现象出现的时间与单体浓度和反应温度呈现明显的相关性。通过数据对比证实了这种流变行为是由于Cis-P_3与副产物P_4的开环活性差异太大,以至于当Cis-P_3开环基本完成后,体系中存在大量活性种与P_4组成的相对稳定的支化状结构缔合物,进而导致体系G’下降。通过流变研究和对所得聚甲基苯基环硅氧烷(PMPS)的~1H-NMR分析发现,极性溶剂中聚合与本体聚合相比,Cis-P_3在二苯基乙烷(DPE)中聚合,可获得更高规整度的PMPS。此外,提出了DPE中通过π-π堆积效应实现稳定Cis-P_3开环聚合中构象和提高PMPS立构规整度的作用机理。The bulk and solution ring opening polymerization of cis-2,4,6-trimethyl-2,4,6, triphenylcyclotri-siloxane (Cis-P 3) ring-opening polymerizations catalyzed by tetramethylammonium (TMAH) were studied by rheometer and 1H-NMR to monitor the changes of storage modules ( G ’), viscosity and chemical structure. A typical rheological phenomenon that G ’of the reaction system firstly decreases then increases is observed in the bulk polymerization of Cis-P3 polymerization. The NMR spectra of the products at the G ’turning-over point moment indicate that the phenomenon is a result of the transition complex composed of polymethylphenylsioxane( PMPS) and P 4(a by-product of Cis-P3 polymerization).Same rheological phenomena with the same occurring time were also observed in P 4 polymerization at different initiation concentrations. The rheological results at different reaction temperature or different monomer concent ration indicate that the occurring time of the phenomenon is dependent on the Cis-P3 polymerization rate. Comparison analysis indicates the special rheological phenomenon is due to the large activity difference between Cis-P3 and P4, which makes the transition complex composed of PMPS and P 4 stable even when the Cis-P 3 is completely ring opened. As a result of the complex accumulation, the G ’of reaction system decreases. It is found that the PMPS polymerized in the solvent with multiple phenyl groups such as diphenylethane( DPE) contributes to a higher stereo-regularity than that in polar solvent (N, N-dimethylformamide (DMF)). The analysis of NMR on the product in DPE, DMF and xylene indicates that the PMPS polymerized in DPE contains more meso-meso structures than those in DMF and xylene. Based on the results, it is deduced that the stabilization of DPE π-π stacked on the transition complexes leads to the improvement of regularity of PMPS.

关 键 词：顺式2 4 6-三甲基-2 4 6-三苯基环三硅氧烷 开环聚合 流变学 立构选择性 

分 类 号：TQ316.341[化学工程—高聚物工业]