Whatever the chemistry used for the synthesis of aliphatic polycarbonates, in particular, those of high molar mass, the adventitious presence of water leads to bimodal GPC traces and affords polycarbonate samples of uncontrolled and unpredictable molar masses. It appears that among all reagents used in the copolymerization of CO₂ and epoxides, CO₂ is the most difficult one to dry. To address this issue, triisobutylaluminum (TiBA) was employed in this work to dry CO₂ through a bubbling method; its drying capability was investigated in the context of the copolymerization of CO₂ with epoxides initiated by onium chloride in the presence of triethylborane (TEB). It was then compared to the efficiency of other already reported drying agents such as phosphorus pentoxide, molecular sieves and commercially available CO₂ purifiers. With TiBA-dried CO₂, its copolymerizations respectively with propylene oxide (PO) and cyclohexene oxide (CHO) could be successfully achieved in a wide range of degrees of polymerization (DP), with the value of DP as high as 16000. Diblock copolymers poly(propylene carbonate-b-cyclohexene carbonate) (PPC-b-PCHC) could also be prepared through sequential addition of epoxide monomers. The polycarbonates obtained under the conditions were all well-defined as characterized by NMR, GPC, triple detector-GPC, and differential scanning calorimetry (DSC).

中文翻译：

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通过环氧化物与 CO2 的阴离子共聚制备单峰超高摩尔质量聚碳酸酯均聚物和二嵌段共聚物

无论用于合成脂肪族聚碳酸酯的化学物质，特别是高摩尔质量的那些，水的偶然存在会导致双峰 GPC 痕量，并提供摩尔质量不受控制和不可预测的聚碳酸酯样品。看来，在用于 CO ₂和环氧化物共聚的所有试剂中，CO ₂是最难干燥的一种。为了解决这个问题，本工作采用三异丁基铝（TiBA）通过鼓泡法干燥CO _{2 ；在CO 2}共聚的背景下研究其干燥能力在三乙基硼烷 (TEB) 存在下，用鎓氯化物引发的环氧化物。然后将其与其他已报道的干燥剂（如五氧化二磷、分子筛和市售的 CO ₂净化器）的效率进行比较。使用TiBA干燥的CO ₂，​​其分别与环氧丙烷（PO）和环氧环己烯（CHO）的共聚可以在很宽的聚合度（DP）范围内成功实现，DP值高达16000。聚（碳酸亚丙酯-b-环己烯碳酸酯）（PPC- b-PCHC) 也可以通过顺序添加环氧化物单体来制备。在该条件下获得的聚碳酸酯均通过 NMR、GPC、三重检测器-GPC 和差示扫描量热法 (DSC) 进行了明确定义。