Base initiated depolymerization of polycarbonates to epoxide and carbon dioxide co-monomers: a computational study
Base initiated depolymerization of polycarbonates to epoxide and carbon dioxide co-monomers: a computational study
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DOI：
10.1039/c3gc40475g
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发表时间：
2013-01-01
期刊：
影响因子：
9.8
通讯作者：
Wei, Sheng-Hsuan
中科院分区：
文献类型：
--
作者：
Darensbourg, Donald J.;Yeung, Andrew D.;Wei, Sheng-Hsuan
高精度CBS-QB 3（+）计算用于获得几种感兴趣的聚碳酸酯进行醇盐回咬以得到相应的环氧化物和二氧化碳的自由能垒。对于大多数聚合醇盐，环氧化物形成的自由能势垒是适度的（12.7-17.4 kcal mol（-1）），并且它们高于产生环状碳酸酯的相同起始材料（10.7-14.6 kcal mol（-1））。聚（环戊烯碳酸酯）不同：环氧化物形成的自由能垒（13.3 kcal mol（-1））低于环状碳酸酯形成的自由能垒（19.9 kcal mol（-1））。这些结果解释了为什么聚（碳酸环戊烯酯）解聚环戊烯氧化物时，用强碱处理，而丙烯和苯乙烯聚碳酸酯解聚到各自的环状碳酸酯。通过单体再生进行回收是生产最高质量材料的理想方法。
High-accuracy CBS-QB3(+) calculations were used to obtain the free energy barriers for several polycarbonates of interest to undergo alkoxide back-biting to give the corresponding epoxide and carbon dioxide. Free energy barriers to epoxide formation were modest for most polymeric alkoxides (12.7-17.4 kcal mol(-1)), and they were higher than for the same starting material to give cyclic carbonate (10.7-14.6 kcal mol(-1)). Poly(cyclopentene carbonate) differs: epoxide formation has a lower free energy barrier (13.3 kcal mol(-1)) than cyclic carbonate formation (19.9 kcal mol(-1)). These results explain why poly(cyclopentene carbonate) depolymerizes to cyclopentene oxide when treated with a strong base, whereas propylene and styrene polycarbonates depolymerize to their respective cyclic carbonates. Recycling via regeneration of the monomer represents the ideal method for producing material of the highest quality.