Synthesis of branched polysiloxanes with controlled branching and functionalization by anionic ring-opening polymerization
Synthesis of branched polysiloxanes with controlled branching and functionalization by anionic ring-opening polymerization
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DOI：
10.1021/ma025920b
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发表时间：
2003-06-03
期刊：
影响因子：
5.5
通讯作者：
Rózga-Wijas, K
中科院分区：
文献类型：
--
作者：
Chojnowski, J;Cypryk, M;Rózga-Wijas, K
合成了具有星形支化、梳形支化和树枝状支化拓扑结构的支化聚硅氧烷。通过使用接枝技术（ACS Polym.准备2001，42，227; ACS Symp. 2003，838，第2章）。研究了乙烯基取代环三硅氧烷（ViMeSiO）（3），V-3和ViMeSiO（SiMe_2O）（2），VD_2的活性阴离子开环聚合（ROP），以及这些单体与六甲基环三硅氧烷（D-3）的共聚反应。终止活性聚合物，具有锂硅烷醇盐端基，在含有SiCl基团的反应性核导致活性聚硅氧烷接枝在核上。通过与Me 2 HSiCl氢化硅烷化将聚合物中的乙烯基转化为反应性SiCl基团使得连续一代支链的接枝成为可能。通过单体V-3和VD 2的聚合，分别获得了前体乙烯基的高密度和低密度的反应性嵌段。均聚导致乙烯基沿着链的均匀密度，而V-3或VD 2与D-3的共聚合产生密度沿链增长方向降低的梯度分布。这种排列导致支链大分子外部的乙烯基密度更高。V-3与D-3在四氢呋喃中由BuLi引发的共聚反应动力学研究表明，反应活性系数k（V ~ 3）= 17.8，k（D ~ 3）= 0.036（25 ℃），由此可确定反应性嵌段中乙烯基的密度分布。以（MeCl_2SiCH_2）（2）为核，得到了四臂星星型共聚物，而用Me_2HSiCl处理的ViMeSiO和Me_2SiO的线性共聚物得到了梳状聚硅氧烷。以官能化的星形聚硅氧烷为核，得到了第一代和第二代树枝状聚硅氧烷。
Functionalized branched polysiloxanes with star-branched, comb-branched and dendritic-branched topologies were synthesized. The branched macromolecules were generated by coupling of reactive blocks using a grafting technique (ACS Polym. Prepr. 2001, 42, 227; ACS Symp. Ser. 2003, 838, Chapter 2). The living anionic ring-opening polymerization (ROP) of vinyl-substituted cyclotrisiloxanes (ViMeSiO)(3), V-3, and, ViMeSiO(SiMe2O)(2), VD2, and the copolymerization of these monomers with hexamethylcyclotrisiloxane, D-3, was explored to obtain reactive blocks. Termination of the living polymer, having a lithium silanolate end group, on a reactive core containing SiCl groups led to the grafting of living polysiloxane on the core. Transformation of vinyl groups in the polymer into the reactive SiCl groups by hydrosilylation with Me2HSiCl made possible the grafting of a successive generation of branches. The reactive blocks of high and low density of the precursor vinyl group were obtained by the polymerization of monomers V-3 and VD2, respectively. While the homopolymerization led to a uniform density of vinyl groups along the chain, the copolymerization of V-3 or VD2 with D-3 produced a gradient distribution with the density decreasing in the direction of the chain growth. This arrangement led to a higher density of the vinyl group in the external part of the branched macromolecule. Study of kinetics of the copolymerization Of V-3 with D-3 in THF initiated by BuLi gave the reactivity coefficients k(v3) = 17.8, k(D3) = 0.036 (25 degreesC), from which the density distribution of vinyl groups in reactive blocks may be determined. Four-arm star copolymers were obtained using (MeCl2SiCH2)(2) as the core, whereas the comblike polysiloxane was obtained from a linear copolymer of ViMeSiO and Me2SiO treated with Me2HSiCl. Dendritic polysiloxanes of the first and second generation were obtained using the functionalized starlike polysiloxane as the core.