丙烯酸甲酯与醋酸乙烯酯的种子乳液聚合

SEEDED EMULSION POLYMERIZATION OF METHYL ACRYLATE ONTO POLYVINYL ACETATE INITIATED BY 2,2\| AZOBISISOBUTYRONITRILE

以过硫酸铵（ＡＰＳ） 为引发剂，合成了粒径分布较均匀的聚醋酸乙烯酯种子乳液（ＰＶＡｃ） ，然后以丙烯酸甲酯（ ＭＡ） 为第二单体和以油溶性偶氮二异丁腈（ＡＩＢＡ） 为引发剂，分别进行不溶胀与溶胀条件下的无皂种子乳液聚合，并用透射电子显微镜（ＴＥＭ） 表征了胶粒形态．表明在不溶胀条件下，胶粒形态随ＰＶＡｃ／ ＭＡ 重量比的不同而变化，当ＰＶＡｃ／ ＭＡ 为１／２ 时，形成以ＰＭＡ 为核，ＰＶＡｃ 为壳的胶粒．在溶胀条件下则得到类似互穿网络型乳胶粒．

Seed latex particles of polyvinyl acetate(PVAc) with narrow diameter distribution were first prepared by using ammonium persulfate as initiator, then unswelling and swelling seeded emulsion polymerization of methyl acrylate(MA) onto PVAc initiated by 2,2′\|azobisisobutyronitrile(AIBN) were carried out at 60℃ in the absence of emulsifier. In order to investigate particle morphologies of various seeded latexes, a selective staining technique using phosphotungstic acid(PTA) was used under transmission electron microscopy(TEM) observation. Results showed that experimental particle size agree roughly with calculated particle size for all of seeded emulsion polymerizations, but particle morphologies are different. Under unswelling condition, taking into account the high water solubility of MA, its homonucleation in water was significant, and PMA secondary particles were formed and coagulated onto the PVAc particles, so initiation and polymerization loci of MA were both in PVAc seed particle and in water phase, and PMA domains were observed at the surface and inside of seeded latex particles when PVAc/MA weight ratios are 2 and 1. When PVAc/MA weight ratio decrease to 0.5,PMA\|PVAc core\|shell particle was observed. While under swelling condition, the inner of PVAc particle swelled with MA was main loci of initiation and polymerization of MA, no PMA domains or core\|shell structure were observed, and interpenetrating network structures were formed for different PVAc/MA ratios.