摘要
以疏水性单体苯乙烯 (St)与较大亲水性单体甲基丙烯酸甲酯 (MMA)的无皂乳液共聚合 ,研究共聚单体组成的变化对聚合动力学和成核机理的影响。结果表明 ,聚合速率随 MMA摩尔分率 f MMA的增大而增大。在较低的f MMA下 ,离子强度的变化对产物乳胶粒径的影响较大 ,随着 f MMA的增大 ,离子强度对乳胶粒直径的影响逐渐变小 ,这证实了共聚合体系中同时存在着均相成核和胶束成核两种机理 ,随着 f MMA增大 ,均相成核的倾向增大而胶束成核的倾向减小。而且发现 ,当 f MMA变化时 ,粒径对引发剂浓度的依赖性十分敏感 ,而对单体总浓度和总离子强度的依赖性很小。它表明 ,无皂乳液的稳定性强烈地依赖于引发剂浓度和极性单体在共聚物中的组成分率。
The soap free emulsion copolymerization of hydrophobic monomer styrene(St) and more water soluble monomer methyl methacrylate(MMA) was carried out. The effects of various monomer compositions on copolymerization kinetics and mechanism of nucleation were investigated. It was shown that the copolymerizaiton rates increase with molar fraction of MMA( f MMA ) increasing. In the lower f MMA , ionic strength affects strongly the diameter of latex particles, but with increasing f MMA , the effect of ionic strength on the diameter become smaller. This implies that there are two nucleation mechanism of homogeneous and oligomer micellar. With f MMA increasing, the possibility of homogeneous nucleation increase and that of micellar nucleation decreases. Moreover, the dependence of diameter of latex particles on initiator concentration varies sharply with different f MMA , but weakly on the total monomer concentration and ionic strength. It indicates that stability of the soap free emulsion dependents strongly on both initiator concentration and composition fraction of polar monomer in the copolymer.
出处
《高分子材料科学与工程》
EI
CAS
CSCD
北大核心
2000年第1期46-48,52,共4页
Polymer Materials Science & Engineering
关键词
乳液聚合
苯乙烯
甲基丙烯酸甲酯
成核
动力学
soap free emulsion copolymerization
styrene
methyl methacrylate
mechanism of nucleation
