几种不可逆加成-断裂型链转移剂在苯乙烯乳液聚合中的研究

Emulsion polymerization of styrene using different chain transfer agents based on the irreversible addition-fragmentation mechanism

研究了基于不可逆加成-断裂链转移机理的3种分子质量调节剂对苯乙烯乳液聚合的影响。主要考察了3种链转移剂对乳液聚合速率、乳胶粒子大小以及聚苯乙烯数均相对分子质量的影响。链转移剂的内在动力学、扩散和自由基解吸附行为决定了其分子质量调节效率、对聚合速率的影响程度和乳胶粒子大小。链转移常数高的α-苯磺酰甲基丙烯酸乙酯使苯乙烯乳液聚合速率下降明显,乳胶粒子粒径分布较宽,且聚合后期不能有效调节聚苯乙烯分子质量;而链转移常数相对较小的2,3-二氯丙烯对聚合速率和乳胶粒子粒径的影响轻微,并能全程控制聚苯乙烯分子质量;分子质量较大的正十二烷基-2-苯基烯丙基硫则因在乳液体系中的扩散较慢,难以调节聚苯乙烯的分子质量。

The emulsion polymerization of styrene with three different chain transfer agents （CTAs） based on irreversible addition-fragment transfer （AFCT） mechanism was carried out. The in-fluences of these irreversible AFCT agents on the rate of polymerization,latex particle size and molec-ular weight of polystyrene were investigated. It was found that the intrinsic activity,diffusion and de-sorption behaviors of the CTAs determined the efficiency of molecular weight control, rate of polymer-ization and particle size in the emulsion polymerization. It has been demonstrated that ethyl α-benzene-sulfonyl-methyiacrylate with high chain transfer constant decreased the reaction rate and particle size, meanwhile,the molecular weight of the polymers could not be controlled well,whereas 2,3-dichloro-propene with low chain transfer constant had a slight effect on the polymerization rate and particle size. It can control the molecular weight fairly well over the whole conversion range in emulsion poly- merization of styrene. Dodecyl（2-phenylallyl）sulfane failed to control the molecular weight,which was attributed to the low rate of diffusion through monomer droplets to aqueous phase in the emulsion pol- ymerization system.