Polyampholyte Microgels with Anionic Core and Cationic Shell

Abstract

We report synthesis of amphoteric microgels by copolymerization of <i>N</i>-vinylcaprolactam (VCL), itaconic acid dimethyl ester (IADME), and vinylimidazole (VIm) in the precipitation−polymerization process. After hydrolysis of ester groups of IADME, component microgels contain acidic and basic groups in their structure. Proton high-resolution transverse magnetization relaxation under magic angle sample spinning (MAS) was used to measure the dynamic heterogeneity corroborated with the chemical structure of a multicomponent amphoteric microgel. NMR results indicate that itaconic acid groups (originated from hydrolyzed IADME component) are localized mostly in the microgel core. The core−shell morphology of poly(<i>N</i>-vinylcaprolactam)-based microgels was suggested with carboxylic acid groups in the core and imidazole groups in the shell. The variation of the IADME and VIm content in microgel structure allows varying microgel charge and swelling degree in basic and acidic pH, respectively. Obtained amphoteric microgels exhibit narrow size distribution and superior colloidal stability.