Effects of monomer polarity on MMA/BA/NaMA emulsifier-free emulsion copolymerization
Effects of monomer polarity on MMA/BA/NaMA emulsifier-free emulsion copolymerization
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DOI：
10.1016/s0014-3057(97)00272-3
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发表时间：
1998-09
影响因子：
6
通讯作者：
Mao-gen Zhang;Z. Weng;Zhi-ming Huang;Z. Pan
中科院分区：
文献类型：
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作者：
Mao-gen Zhang;Z. Weng;Zhi-ming Huang;Z. Pan
研究了甲基丙烯酸甲酯(MMA)和丙烯酸正丁酯(BA)在少量甲基丙烯酸钠(NaMA)存在下，以过硫酸钾为引发剂在70℃下进行的无乳化剂乳液共聚反应。增加BA进料比例会导致乳液粒径、表面张力和粘度降低，而颗粒数、聚合速率、乳液表面电荷密度和共聚物平均分子量增加。 MMA/NaMA无乳化剂乳胶共聚物(EFLC)的DSC热分析图显示1个玻璃化转变温度(Tg)，BA/NaMA EFLC显示2个Tg，MMA与BA重量比在2:1-1:2之间的MMA/BA/NaMA EFLC显示4个Tg。多个 Tg 下共聚物组成的不均匀性归因于组成差异和相分离，因为颗粒周围亚层中的溶解水富含 –OSO3− 和 –COO− 基团，导致 BA 向颗粒核心扩散，MMA 向外扩散。
The emulsifier-free emulsion copolymerizations of methyl methacrylate (MMA) and n-butyl acrylate (BA) in the presence of a small amount of sodium methacrylate (NaMA) with potassium persulfate as initiator at 70°C were investigated. Increasing BA feed fraction causes the decrease of particle diameter, surface tension and viscosity of the latices, and the increase of particle number, polymerization rate, surface charge density of the latices and average molecular weight of copolymers. The DSC thermograms of MMA/NaMA emulsifier-free latex copolymer (EFLC) shows one glass transition temperature (Tg), that of BA/NaMA EFLC shows two Tgs, and those of MMA/BA/ NaMA EFLCs with the weight ratio of MMA to BA within 2:1–1:2 show 4 Tgs. The heterogeneity of copolymer composition for multiple Tgs is ascribed to the composition difference and phase separation, since the dissolved water in the sublayer surrounding the particle, enriched with –OSO3−and –COO−groups, causes the diffusion of BA toward the particle core and that of MMA outward the core.