VAc／St乳液共聚物的相对分子质量及组成分布

Relative molecular mass and composition distribution of VAc/St latex

采用3种加料方式【间歇法、滴加苯乙烯(St)法及滴加预乳化液法】合成乙酸乙烯酯(VAc)/St乳液共聚物。考察了共聚合方式对VAc/St乳液共聚物相对分子质量及其组成分布的影响,间歇法所得乳液共聚物相对分子质量较大,分布较宽;而滴加预乳化液法较小,分布也较窄;滴加St法居中。m(VAc)/m(St)为7:3的乳液共聚物在30℃的四氢呋哺溶剂中Mark-Houwink常数为1.24×10^(-3)mL/g,扩张因子为0.86。

The authors synthesized a kind of emulsion copolymer from vinyl acetate （VAc） and styrene （St） with 3 feeding procedures, i.e. adding initiator in batchwise, adding styrene dropwise and adding pre-emulsion dropwise. The effects of copolymerization mode on molecular mass and composition distribution of the VAc/St latex were explored. The results reveal that the VAc/St latex synthesized by adding initiator in batchwise has the highest relative molecular mass and the widest distribution, whereas the VAc/St latex prepared by adding pre-emulsion dropwise has the lowest corresponding values among the three emulsion copolymers. The VAc/ St latex made by adding styrene dropwise possesses the intermediate values between the two. The VAc/St latex （mass ratio 7 ： 3） in tetrahydrofuran at 30℃ has the Mark-Houwink constant of 1.24×10^-3 mL/g and expansion factor of 0.86.