O/W型微乳液法制备PMMA纳米粒子研究——PMMA粒径及分布、分子量和结构分析

Study on nano-size PMMA particles prepared by O/W microemulsion polymerization —— Particle diameter and its distribution, molecular weight and microstructure of PMMA

采用动态激光光散射(DLS)研究了单体、引发剂和乳化剂用量对微乳液聚合PMMA的粒径及分布、分子量的影响。DLS分析结果表明,PMMA的粒径为25～60nm,M—w为1×106～5×106。随单体用量增大,PMMA粒径变大;随引发剂用量增大,PMMA粒径变小;PMMA粒径分布随单体和引发剂用量提高而变宽。在8%～12%(质量分数)范围内,随乳化剂用量增大PMMA粒径增大,分布变窄,然后随着乳化剂用量的进一步增加,PMMA粒径减小。引发剂用量减少和乳化剂用量增加均使PMMA分子量提高。FT IR和DSC分析结果表明,采用微乳液聚合方法制备的PMMA是以间规立构为主,PMMA分子链的局部有序性得到了提高。

The particle diameter and its distribution, weight average molecular weight ( M—_w), and microstructure of PMMA prepared by microemulsion polymerization were studied by dynamic laser scattering (DLS), FTIR and DSC. The results of DLS showed that the particle diameter ranged from 25nm to 60nm and the range of M—_w was between 1×10~6 and 5×10~6. The particle diameter increased with the monomer concentration increasing and decreased with the initiator concentration increasing. Moreover, its distribution becomes wider. It was clear that there existed a critical concentration of CTAB (12%wt), up to which the particle diameter increase and then decrease thereafter. The M—_w increased with CTAB concentration increasing and KPS concentration decreasing. The FT-IR and DSC results showed the syndiotactic structure was dominant in the structure of PMMA obtained by microemulsion polymerization and the order orientation of PMMA chains was improved.