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首页> 外文期刊>Chemistry: A European journal >Unprecedented polymerization of trimethylene carbonate initiated by a samarium borohydride complex: Mechanistic insights and copolymerization with epsilon-caprolactone
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Unprecedented polymerization of trimethylene carbonate initiated by a samarium borohydride complex: Mechanistic insights and copolymerization with epsilon-caprolactone

机译：硼氢化sa络合物引发的碳酸亚丙酯的前所未有的聚合：机理见解和与ε-己内酯的共聚

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摘要

Poly(trimethylene carbonate) (PTMC) was synthesized through ring-opening polymerization by using a rare-earth borohydride initiator, [Sm(BH4)(3)(thf)(3)]. This initiator shows a high activity to give high-molar-mass PTMCs with molar-mass distributions ranging from 1.2 to 1.4, and with a regular structure void of ether linkages. ne polymers were characterized by H-1 and C-13 NMR spectroscopy, H-1-H-1 COSY, H-1-C-13 HMQC NMR spectroscopy, size-exclusion chromatography (SEC), viscosimetry, and MALDI-TOF MS analyses. A coordination-insertion mechanism was established based on detailed NMR characterizations, especially of the polymer chain end-functions. The monomer initially coordinates the samarium to give [Sm(BH4)(3-)(tMc)(3)], 1. The monomer then opens up through cleavage of the cyclic ester oxygen-acyl bond and inserts into the Sm-HBH3 bond resulting in an alkoxide complex, [Sm{O(CH2)(3)OC(O)HBH3}(3)], 2, or [Sm{O(CH2)(3)OC(O)H)(3)], 2', which then propagates the polymerization of TMC to give the active polymer [Sm({O(CH2)(3)OC(O)(n)-O(CH2)(3)OC(O)HBH3)(3)], 3 or [Sm(O(CH2)(3)OC(O){O(CH2)(3)OC(O)}(n)O- (CH2)(3)OC(O)H)(3)], 3'. Finally, acidic hydrolysis of 3 or 3' gives HO-(CH2)(3)OC(O)[O(CH2)(3)OC(O)](n)O-(CH2)(3)OC(O)H, 4. This novel alpha-hydroxy w-formatetelechelic PTMC represents the first example of a formate-terminated polycarbonate. TMC and epsilon-caprolactone (CL) were copolymerized to afford both random PTMC-co-PCL and block PTMC-b-PCL copolymers that were characterized by H-1 NMR spectroscopy, SEC, and differential scanning calorimetry (DSC). The structure of the block copolymers depends on the order of addition of monomers: if CL is introduced first, dihydroxytelechelic HO-PTMC-b-PCL-OH polymers are formed, whereas introduction of TMC first or simultaneous addition of comonomers leads to hydroxyformatetelechelic HC(O)O-PTMC-b-PCL-OH analogues.
机译：使用稀土硼氢化物引发剂[Sm（BH4）（3）（thf）（3）]通过开环聚合反应合成聚碳酸三亚甲基酯（PTMC）。该引发剂显示出高活性，可得到摩尔质量分布范围为1.2至1.4且具有规则结构的无醚键的高摩尔质量PTMC。通过H-1和C-13 NMR光谱，H-1-H-1 COSY，H-1-C-13 HMQC NMR光谱，尺寸排阻色谱（SEC），粘度测定法和MALDI-TOF MS表征聚合物分析。基于详细的NMR表征，特别是聚合物链末端官能团，建立了配位插入机制。单体首先与the配位，得到[Sm（BH4）（3-）（tMc）（3）]，1。然后，该单体通过环状酯氧-酰基键的裂解而打开，并插入Sm-HBH3键中生成醇盐配合物[Sm {O（CH2）（3）OC（O）HBH3}（3），2或[Sm {O（CH2）（3）OC（O）H）（3）] ，2'，然后传播TMC的聚合，得到活性聚合物[Sm（{O（CH2）（3）OC（O）（n）-O（CH2）（3）OC（O）HBH3）（3 ）]，3或[Sm（O（CH2）（3）OC（O）{O（CH2）（3）OC（O）}（n）O-（CH2）（3）OC（O）H）（ 3）]，3'。最后，酸水解3或3'得到HO-（CH2）（3）OC（O）[O（CH2）（3）OC（O）]（n）O-（CH2）（3）OC（O） H，4。这种新颖的α-羟基w-甲酰胺基PTMC代表了甲酸酯封端的聚碳酸酯的第一个例子。将TMC和ε-己内酯（CL）共聚，以提供无规PTMC-co-PCL和嵌段PTMC-b-PCL共聚物，这些共聚物均通过H-1 NMR光谱，SEC和差示扫描量热法（DSC）表征。嵌段共聚物的结构取决于单体的添加顺序：如果先引入CL，则会形成二羟基长寿HO-PTMC-b-PCL-OH聚合物，而先引入TMC或同时加入共聚单体会导致羟基甲醚化HC（ O）O-PTMC-b-PCL-OH类似物。

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