单分散交联聚（4—乙烯吡啶／丙烯酸丁酯）无皂正电性共聚乳胶

以偶氮二异丙基脒盐酸盐（V50)为引发剂，采用4－乙烯吡啶（4－VP）／丙烯酸丁酯（BA）为混合单体，分别以二乙烯苯（DVB）或双甲基丙烯酸乙二醇酯（EGDMA）为交联剂，用无皂乳液聚合的方法合成了一系列正电性共聚乳液，并用扫描电镜（SEM）、Zeta电位测定仪详细研究了单体配比、交联剂种类和交联度对粒径大小及其分布、粒子形态和乳液电性能的影响，并探讨了该三元无皂乳液聚合的成核机理。结果表明：4VP／BA的无皂乳液聚合遵循均相成核机理。当BA含量低或者微球交联度较小时，高分子亲水性强，临界链长度大，生成粒子数目少，所以粒径大；随着BA含量的增加或者交联度的增大，高分子疏水性增强，临界链长度沽小，生成粒子数目增多，粒径变小，当BA／4VP＝1／4（g/g)时，得到单分散共聚乳胶，少量BA与4VP共聚可以明显提高乳液的稳定性。

MONODISPERSE CROSSLINKED POLY (4-VINYLPYRIDINE-CO-BUTYL ACRYLATE) SOAPLESS CATIONIC LATEXES

A series of cationic latex were synthesized via an emulsifier-free emulsion polymerization, using 2,2'-azobis-2(amidineopropane)dihydrochloride (V50) as initiator, 4-vinylpyridine (4-VP) and butylacrylate (BA) as comonomers, divinylbenzene (DVB) or ethylene glycol dimethacrylate (EGDMA) as cross-linker, respectively. The influence of co-monomer ratio, cross-linking degree of different cross-linker on the particle size and its distribution, the morphology and electric properties of the resultant latex were studies in a great details by Scanning Electron Microscopy (SEM) and zeta potential analyzer. The results indicate that the soapless emulsion polymerization of 4VP/BA followed homogeneous nucleation mechanism. As the ratio of BA to 4VP or the crosslinking degree increased, the hydrophobility of polymer decreased; therefore, the critical chain length got shorter, causing lower growing particle number. As a result, the diameter of the particles became smaller. The colloidal stability of the latex was improved by adding adequate amount of BA. Most stable latex with narrow size distribution was obtained when BA/4VP ratio was 1/4(g/g).