Abstract:

A batch-semi-batch two-stage reversible addition-fragmentation chain transfer(RAFT) mini-emulsion polymerization of styrene was investigated.It was found that the starting point of the feeding stage (the semi-batch stage) and the solid content of the final latex were critical to reducing the amount of coagulum.The monomer feeding of the second stage should start after monomer conversion 40% of the first stage and the solid content of the final latex should remain below 40%.Under such conditions little coagulum was observed.It was concluded that the two-stage semi-batch RAFT mini-emulsion polymerization was effective to synthesize higher molecular weight polymer (～8×10⁴ g•mol^-1) with narrow molecular weight distribution (PDI=～1.3) and low residues of the surfactant and co-stabilizer (～1.5%,mass).

Key words: 活性自由基聚合, RAFT聚合, 细乳液聚合, 半连续聚合

摘要：

进行了苯乙烯的间歇-半连续RAFT细乳液聚合，考察了半连续段的起点、单体滴加速率及最终胶乳固含量的影响。结果发现：从最终胶乳的稳定性考虑，半连续聚合的起点选择在间歇聚合的高转化率时期更好;若综合考虑胶乳的稳定性、分子量及其分布、固含量、乳化剂及共稳定剂在胶乳中的残留率等因素，半连续聚合的起点可适当提前，但必须在间歇聚合成核期结束后。过早容易引起乳液的失稳;过迟会延长反应时间，降低聚合物的制备效率，导致死聚物链含量升高。聚合体系的稳定性与胶乳的固含量密切相关，最终固含量不宜超过40％。采用间歇-半连续二段聚合工艺可以制得窄分子量分布(PDI＝～1.3)，低乳化剂及共稳定剂残留量（～1.5%，质量）的高分子量聚合物(≈8×10⁴g•mol^-1)。

关键词: 活性自由基聚合, RAFT聚合, 细乳液聚合, 半连续聚合