PMMA/CA核壳纳米微粒的制备与表征

PREPARATION AND CHARACTERIZATION OF PMMA/CA CORE/SHELL NANOPARTICLES

采用乳液聚合方法,不使用任何乳化剂,将甲基丙烯酸甲酯(MMA)在干酪素(CA)存在下使用叔丁基过氧化氢为引发剂,通过接枝聚合制备了直径在150 nm左右的具核壳结构的PMMA/CA纳米复合乳胶粒,乳胶粒的核壳结构通过透射电镜得到了证实.探讨了反应温度、引发剂用量、核壳质量比等条件对单体转化率和接枝效率的影响.阐明了制备此类复合乳胶粒的实验条件,对其形成机理进行了较深入的探讨.

With no any surfactant and in the presence of casein（CA）,nano-sized core /shell latex particles based on methyl methacrylate（MMA） /CA with about 150 nm in diameter,determined by light scattering,were prepared through emulsion polymerization of MMA using tert-butyl hydroperoxide（TBHP） as initiator.The designed core-shell structure was confirmed by TEM observation.Results revealed that a sharp decrease in particle size was observed within the first 20 min of the polymerization,and the particle size remained quite constant afterwards.Monomer conversion reached about 70% within 30 min of the initiationf,ollowed by a very slow increase to about 73% up to 3 h of polymerization.Optimization of the polymerization process demonstrated thatt,o achieve high MMA conversion,high PMMA grafting on CA and relatively narrow size distribution for the core-shell particles,polymerization temperature should be kept between 70℃ and 80℃,TBHP level at 0.18% to 0.36% of CA mass,MMA /CA ratios at 4 /1 by mass and total content of MMA and CA not higher than 10% by weight in the system.Under these conditions,core-shell particles of PMMA-CA with MMA conversion ≥75% and PMMA grafting on CA ≥75% were achieved.The results were interpreted based on the mechanism of the initiation and particle formation.