硫代羰基化合物中Z和R基团结构对苯乙烯RAFT聚合的影响

为了考察RAFT试剂中取代基对其聚合控制性能的影响,合成了具有不同Z基团和R基团结构的二硫代酯化合物,同时合成了具有不同Z基团结构的二硫代氨基甲酸酯化合物,并将这些化合物作为链转移剂,以AIBN为引发剂进行了苯乙烯70℃下的RAFT聚合,考察了Z基团和R基团对这些化合物在苯乙烯自由基聚合中的控制性能。通过测定链转移常数考察了Z基团和R基团对此类化合物在用于RAFT聚合时控制性能差异的现象。结果显示RAFT试剂中Z基团和R基团的结构对其控制性能和链转移常数有很大的影响。当在Z基团中引入共轭结构后可以明显改善其用于苯乙烯聚合的控制性能,链转移常数也有相同的趋势。RAFT试剂中在控制苯乙烯自由基聚合时异丁酸酯基是最有效的R基团,异丁腈酯基次之,而异丙苯基最差。使用二硫代氨基甲酸酯类化合物作为链转移剂进行苯乙烯的自由基聚合过程的结果显示当氮原子处于共轭结构中,可以有效地控制苯乙烯聚合。而当氮原子不处于共轭结构中不能有效的控制苯乙烯自由基聚合。

The effect of Z and R structures in dithiocarboxylic compounds on RAFT polymerization of styrene

Dithiocarboxylic compounds with different R and Z groups have been synthesized. The dithiocarbamates with different Z groups have been synthesized at the same time. Using these compounds as the chain transfer agents and AIBN as the initiator, the RAFT polymerization of styrene has been carried out at 70 ℃. The control properties of the polymerization using different ditho compounds with different R and Z groups as the RAFT agent have been investigated. The chain transfer constant of these dithio compounds with different R and Z groups have been measured. Furthermore, the relationships between the chain transfer constant of compound and the control abilities of polymerization have been explored. The results showed that Z and R groups in RAFT agents show great effect on their control abilities and chain transfer constant. The introducing of conjugation structures into Z group of RAFTagent showed positive effect on their control abilities in styrene polymerization. Same tendency can be found in their chain transfer constant. The RAFT polymerization of styrene showed that the isobutanic acid ester group was the most effective group, followed with the isobutyronitrile and cumyl group. As the cases of dithiocarbamates, it showed as effective agent in the polymerization of styrene as nitrogen atom was located among conjugated structures. However, the dithiocarbamates with nitrogen atom didn’t locate among conjugated structures were not the effective control agent in the polymerization of styrene.