双硫酯作为链转移剂的苯乙烯本体聚合研究

研究了二硫代苯甲酸苄基酯（BDB）、二硫代苯甲酸苯乙基酯（PEDB）及二硫代苯甲酸异丙苯基酯（CDB）三种RAFT试剂作为链转移剂的苯乙烯本体聚合。动力学研究表明，当BDB及PEDB浓度和偶氮二异丁腈（AIBN）浓度同时增大时，AIBN浓度提高所导致的聚合反应速率提高起主导作用：当CDB和AIBN浓度同时提高时，CDB浓度提高所导致的聚合速率降低作用影响更显著。对CDB体系，随转化率提高分子量分布变宽。对BDB体系，当其浓度较高时，随转化率提高分子量分布变窄；当其浓度较低时，不利于实现可控，活性聚合，反应后期分子量分布变宽。动力学和GPC分析均表明以BDB为链转移剂时苯乙烯本体聚合的可控性最好。在同时考虑链转移剂和引发剂作用的基础上，提出了修正的聚合物分子量预测模型，该模型可有效预测以双硫酯为链转移剂的苯乙烯RAFT聚合体系的分子量。

Study on Bulk Polymerization of Styrene with Dithioester as Chain Transfer Agent

The bulk polymerizations of styrene were studied in detail by using AIBN as initiator and using benzyl dithiobenzoate (BDB), 1-phenylethyl dithiobenzoate (PEDB) and cumyl dithiobenzoate (CDB) as chain transfer agents, respectively. The experiments show that when the concentrations of AIBN and RAFT agent are increased, the polymerization rate increases for both BDB/AIBN/St and PEDB/AIBN/St systems, but decreases for the CDB/AIBW/St system. And the experimental results indicate that for BDB/AIBN/St and PEDB/AIBN/St system the effect of initiator on polymerization plays a primary role, but for CDB/AIBN/St system the effect of RAFT agent on polymerization is dominant. In CDB system, the molecular weight distribution of polymer becomes broader along with raising the monomer conversion. But in BDB system molecular weight distribution gets narrower with raising the monomer conversion under the high BDB concentration, while, if the BDB concentration is low, the polymerization can not be controlled effectively and the molecular weight contribution becomes broader in the final stage. The results of kinetic study and GPC analysis both show that the bulk polymerization of styrene can be controlled effectively when BDB is used as chain transfer agent. By considering the combined effects of RAFT agents and initiator, a revised model for predicting molecular weight was proposed, which can be used to predict the polymer molecular weight of bulk polymerization of styrene with dithioester as chain transfer agents.