聚甲基丙烯酸基纳米水凝胶的“绿色”合成

“Green”Synthesis of Poly( methacrylic acid)-based Nano-hydrogels

利用原位生成的聚甲基丙烯酸甲酯种子乳胶模板以及表面活性剂与功能单体间的正负电荷作用,发展了一种可在全水相中"绿色"合成聚甲基丙烯酸(PMAA)基纳米水凝胶的新方法.利用动态光散射法、ζ-电位测定、FTIR和TEM对纳米水凝胶的尺寸及其分布、表面电荷、组成、形态、结构和p H响应行为进行了表征.结果表明,PMAA基纳米水凝胶具有聚甲基丙烯酸甲酯内核和交联聚甲基丙烯酸外壳的核壳结构.当甲基丙烯酸(MAA)的用量由2 m L增至3 m L时,PMAA基纳米水凝胶的尺寸变大.当MAA的用量增加至5 m L时,反应体系中除了生成PMAA基纳米水凝胶外,还生成了PMAA次级粒子.PMAA基纳米水凝胶表现出良好的p H响应性:当介质的p H值由2增加至7时,其流体力学体积扩张了近80倍.

Due to the water-solubility of poly（ methacrylic acid）（ PMAA）,it is hard to synthesize PMAA nanoparticles in water phase. A novel method for the ＂green ＂synthesis of PMAA-based nano-hydrogels in water phase was developed. In the method,small poly（ methyl methacrylate）（ PMMA） nanolatex particles formed ＂in situ＂were used as the seeds. Meanwhile,the electrostatic interactions between the surfactants on the surfaces of the seeds and MAA monomers were utilized to realize the selective polymerization of MAA on the surfaces of the PMMA seeds,thus resulting in the formation of PMAA-based nano-hydrogels with PMMA cores and cross-linked PMAA shells. The size and size distribution,surface charges,composition,morphology,structure and p H-response behavior of the resulting nano-hydrogels were characterized by dynamic light scattering,ζ-potential measurement,Fourier transform infrared spectroscopy（ FTIR）,and transmission electron microscopy（ TEM）. The core-shell structure of the PMAA-based nano-hydrogels was disclosed by TEM observations. The size of the PMAA-based nano-hydrogels increases as the amount of MAA increases from 2 m L to 3 m L. However,as the amount of MAA increases to 5 m L,besides the PMAA-based nano-hydrogels,small pure PMAA nanoparticles also appear. Finally,the PMAA-based nano-hydrogels display excellent p Hresponses： as the p H value increases from 2 to 7,the expansion of their hydrodynamic volumes approaches 80 times.