丙烯酸丁酯碘转移细乳液聚合动力学

Kinetics of Iodine Transfer Miniemulsion Polymerization of Butyl Acrylate

碘转移聚合(ITP)是一种链调控剂易得的可逆失活自由基聚合法,细乳液ITP具有高的链调控剂使用效率和乳液稳定性。以碘仿为链转移剂、2,2’-偶氮二异丁基脒二盐酸盐(AIBA)为引发剂,进行丙烯酸丁酯(BA)细乳液ITP,研究AIBA浓度、碘仿浓度和聚合温度对BA聚合转化率、反应速率、聚丙烯酸丁酯(PBA)平均分子量和分子量分布的影响。结果表明:BA细乳液ITP反应快,前期符合一级反应特征,表观反应速率常数随AIBA浓度增大和聚合温度升高而增大;碘仿浓度对反应速率影响不大,但影响PBA的分子量,当碘仿相对单体的摩尔浓度由1‰降低到0.25‰时,转化率大于90%的PBA的数均分子量由1.2×10^(5)增大到5.0×10^(5)左右。以PBA为大分子调节剂种子乳液进行甲基丙烯酸甲酯(MMA)扩链(其中BA与MMA物质的量比为1:1),成功制备了分子量和乳胶粒子粒径均增大的PMMA-b-PBA-b-PMMA共聚物乳液。聚合动力学研究和聚合物结构表征证实了BA和MMA细乳液聚合的“活性”特征。

Iodine transfer polymerization(ITP)is one kind of reversible-deactivation radical polymerization method using facile chain mediators,and the miniemulsion ITP process can produce high stable polymer emulsions with high chain mediation efficiencies.Butyl acrylate(BA)iodine transfer miniemulsion polymerizations were carried out using 2,2’-azobis(2-methylpropionamidine)dihydrochloride(AIBA)as a initiator and iodoform as a transfer agent,and effects of AIBA concentration,iodoform concentration and temperature on kinetics of BA polymerization were investigated.The reaction of BA iodine transfer miniemulsion polymerization was fast and corresponded to the characteristics of the first-order reaction in early period.Its apparent reaction rates were increased with the increase of AIBA concentration and temperature,and it varied slightly as the iodoform concentration changed.The molecular weights of PBA could be adjusted by the iodoform concentration and polymerization conversion.As the iodoform molar concentration to monomer decreased from 1‰to 0.25‰,the number average molecular weight of PBA was increased from 1.2×10^(5) to 5.0×10^(5) when BA conversion was greater than 90%.PMMA-b-PBA-b-PMMA latex with particles of larger average size and molecular weight was prepared(where the mole ratio of BA and MMA was 1:1)by a chain extension of PBA by methyl methacrylate(MMA)using PBA as a macromolecular mediator and seeded latex particles.Both BA and MMA polymerizations exhibited living nature as evidenced by the kinetics behavior and structure of obtained polymers.