Catalytic Ring-Opening (Co)polymerization of Semiaromatic and Aliphatic (Macro)lactones
Catalytic Ring-Opening (Co)polymerization of Semiaromatic and Aliphatic (Macro)lactones
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DOI：
10.1021/acs.macromol.6b00744
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发表时间：
2016-06-28
期刊：
影响因子：
5.5
通讯作者：
Duchateau, Rob
中科院分区：
文献类型：
--
作者：
Pepels, Mark P. F.;van der Sanden, F.;Duchateau, Rob
研究了铝盐催化下对苯二甲酸丁二酯低聚物开环聚合反应。cBT在四氯乙烷（TCE）中的ROP的动力学分析表明，催化剂的速率常数和单体浓度具有一级依赖性。与其他溶剂中的ROP比较表明，TCE对催化剂的短期可逆失活和长期永久失活均有明显的延缓作用。分别测定了cBT和epsilon-己内酯（CL）的ROP的表观活化能，并利用其反应活性的差异来考察其合成嵌段共聚物的可能性。在一段时间内从单一进料共聚中获得的共聚物序列分布分析表明，在整个反应范围内，随机性程度很高。在连续进料方法中，在cBT聚合完成后加入CL，表明繁殖反应不够快，无法避免酯交换反应，随着时间的推移，生成的共聚物的随机性越来越大。此外，cBT与omega-pentadecalactone （PDL）的共聚在高于聚对苯二甲酸丁二酯（PBT）结晶温度的温度下进行，得到了在聚pentadecalactone （PPDL）和PBT之间的整个组成范围内的无规共聚物。以salen铝为催化剂的共聚反应速度快，分子量高。引入任一组分后，PPDL和PBT的熔融温度均下降，达到50 ~ 70 mol % PDL之间的共晶点。此外，热分析和x射线衍射的结合表明，PDL单元完全排除在PBT晶格之外，而对苯二甲酸丁二酯单元部分纳入PPDL晶格。
The ring-opening polymerization (ROP) of cyclic butylene terephthalate oligomers (cBT) using an aluminum salen catalyst was investigated. The kinetic analysis of the ROP of cBT in tetrachloroethane (TCE) revealed a first order dependence of the rate constant in catalyst as well as monomer concentration. Comparison with the ROP in other solvents showed that TCE significantly retards the reaction by short-term reversible catalyst deactivation and by long-term permanent deactivation. The apparent activation energy for the ROP of cBT and epsilon-caprolactone (CL) were determined independently, and the difference in reactivity was used to investigate the possibility to synthesize blocky copolymers. Sequence distribution analysis of the copolymers obtained over a period of time from a single feed copolymerization revealed that over the full reaction range the degree of randomness was high. A sequential feed approach, in which CL was added after the polymerization of cBT was completed, showed that the propagation reaction was not fast enough to avoid transesterification, yielding copolymers with an increasing degree of randomness over time. Additionally, the copolymerization of cBT with omega-pentadecalactone (PDL) was performed in bulk at temperatures above the crystallization temperature of poly(butylene terephthalate) (PBT), yielding random copolymers over the full composition range between polypentadecalactone (PPDL) and PBT. Copolymerizations using aluminum salen as catalyst were rapid and high molecular weights could be achieved. The melting temperature of both PPDL and PBT decreased upon the introduction of either counit, reaching a eutectic point between 50 and 70 mol % PDL. Furthermore, a combination of thermal analysis and X-ray diffraction shows that PDL units are fully excluded from the PBT crystal lattice, while butylene terephthalate units are partially incorporated into the PPDL crystal lattice.