Institute of Electronic Structure and Laser Foundation for Research and Technology-Hellas, P.O. Box 1527, 711 10 Heraklion, Crete, Greece.
Langmuir. 2010 Jan 19;26(2):639-47. doi: 10.1021/la902231b.
pH-responsive amphoteric core-shell microgel particles were synthesized by emulsion copolymerization of the appropriate functional monomers with ethylene glycol dimethacrylate as the cross-linker. 2-(Diethylamino)ethyl methacrylate (DEA) was used as the ionizable basic monomer, and tert-butyl methacrylate served as the hydrophobic monomer precursor, which gave the methacrylic acid (MAA) moieties following acid hydrolysis of the ester groups. The core of the polyampholyte microgels comprised a cross-linked poly(2-(diethylamino)ethyl methacrylate) (PDEA) or poly(methacrylic acid) (PMAA) network surrounded by a cross-linked PMAA or PDEA shell, respectively. A polyampholyte random copolymer microgel with the DEA and MAA units randomly distributed within the gel phase was also prepared. Scanning electron microscopy studies showed spherical particles of a narrow size distribution, and transmission electron microscopy verified the core-shell topology of the particles. Potentiometric titration curves revealed two plateau regions for the polyampholyte core-shell microgels attributed to the independent ionization process of the core and the shell of the particles, in contrast to the random copolymer microgel particles that exhibited a single plateau region as a result of the simultaneous protonation/deprotonation process of the basic and acidic moieties of the microgels. The core and the shell of the particles were found to swell independently upon ionization of the DEA or MAA moieties at low or high pH, respectively, whereas collapsed latex particles were obtained in the intermediate pH range when both the core and the shell of the particles were neutral, in agreement with the potentiometric titration data. These core-shell microgels comprise novel two-compartment nanostructures that exhibit contraphilic properties in the core and the shell of the particles in response to a single external stimulus.
通过将适当的功能单体与乙二醇二甲基丙烯酸酯作为交联剂进行乳液共聚，合成了 pH 响应两性核壳微凝胶颗粒。2-（二乙基氨基）乙基甲基丙烯酸酯（DEA）用作可离子化的碱性单体，叔丁基甲基丙烯酸酯作为疏水性单体前体，酯基酸水解后得到甲基丙烯酸（MAA）部分。聚两性电解质微凝胶的核由交联的聚（2-（二乙基氨基）乙基甲基丙烯酸酯）（PDEA）或聚（甲基丙烯酸）（PMAA）网络组成，分别由交联的 PMAA 或 PDEA 壳包围。还制备了具有 DEA 和 MAA 单元在凝胶相中随机分布的聚两性电解质无规共聚物微凝胶。扫描电子显微镜研究表明，具有窄粒径分布的球形颗粒，透射电子显微镜证实了颗粒的核壳结构。电位滴定曲线显示，聚两性电解质核壳微凝胶具有两个平台区域，这归因于颗粒的核和壳的独立电离过程，与随机共聚物微凝胶颗粒形成对比，后者由于微凝胶的碱性和酸性部分的同时质子化/去质子化过程而表现出单个平台区域。发现当 DEA 或 MAA 部分离子化时，颗粒的核和壳独立溶胀，分别在低或高 pH 下，而在中间 pH 范围时，当颗粒的核和壳均为中性时，得到塌陷的乳胶颗粒，与电位滴定数据一致。这些核壳微凝胶包含新型两隔室纳米结构，在颗粒的核和壳中表现出反亲水性质，以响应单个外部刺激。
