聚甲基丙烯酸纳米水凝胶的水相合成及其磁性功能化

Poly(methacrylic acid) Nano-hydrogels Synthesized in Water and Their Magnetic Functionalization

利用十二烷基硫酸钠/吐温20复配表面活性剂和原位生成的聚甲基丙烯酸甲酯(PMMA)种子乳胶,发展了一种可在全水相中"绿色"合成较高浓度的聚甲基丙烯酸(PMAA)纳米水凝胶的新方法.以PMAA纳米水凝胶为前驱体,采用原位氧化沉淀法制备了磁性PMAA纳米微球.利用动态光散射法、FTIR分析、TEM观察、振动样品磁强计测试(VSM)、热重分析(TG)等对纳米水凝胶和磁性微球进行了表征,并探讨了PMAA纳米水凝胶的形成机理.结果表明,吐温20与MAA和PMAA间的氢键作用,促成了交联PMAA/吐温20复合物层在PMMA种子乳胶表面的选择性生长,导致生成了具有核壳结构的PMAA纳米水凝胶.PMAA纳米水凝胶表现出良好的p H响应性,当介质的p H值由1增加至6时,其流体力学体积扩张了近50倍.磁性PMAA纳米微球具有超顺磁性,其饱和磁化强度高达50 A·m^2/kg.

A novel method for the ＂green＂ synthesis of PMAA nano-hydrogels in water was developed. In the method,small poly （methyl methacrylate） （PMMA） nanolatex particles formed ＂in situ＂ were used as the seeds. Meanwhile,the hydrogen bonding interactions between the surfactant tween 20 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 nano-hydrogels with PMMA cores and cross-linked PMAA shells. Magnetic PMAA nanoparticles were further fabricated by an ＂in situ＂ oxidization precipitation method. The size and size distribution, composition, morphology, structure, pH-response behavior and magnetic property of the resulting PMAA nano-hydrogels and magnetic PMAA nanoparticles were characterized. The hydrogen bonding interactions between tween 20 and MAA （PMAA） prompt the selective growth of a crosslinked PMAA layer on the surfaces of PMMA seed latex, resulting in the formation of PMAA nano-hydrogels with PMMA cores and cross-linked PMAA shells. The core-shell structure of the PMAA nano-hydrogels was disclosed by TEM observations. The PMAA nano-hydrogels display excellent pH-responses：as the pH value increases from 1 to 6, the expansion of their hydrodynamic volumes approaches 50 times. The magnetic PMAA nanoparticles were superparamagnetic and with a saturation magnetization as high as 50 A·m^2/kg.