Polyampholyte Microgels with Anionic Core and Cationic Shell

Abstract

We report synthesis of amphoteric microgels by copolymerization of N-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(N-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.

Synthesis of polyampholyte microgels from colloidal salts of pectinic acid and their application as pH-responsive emulsifiers

“…However, the flocculated microgels could be easily redispersed by either an increase or a decrease in pH of the medium. We have found that the hydrodynamic diameters of microgels 3c-e, 4b, 5,6, and 7b at pH2 and pH8.5 are almost the same, which is an evidence of the swollen state of the microgels (Table 1). This result is quite similar to the behaviors observed in the cases of other polyampholyte polymers and their gels [4,8].…”

“…In the last years, most attention was paid to polyampholyte microgels, which belong to smart materials due to their response to temperature, pH, ionic strength, water-organic solvent composition, electric field, etc. Various microgels bearing amino and carboxyl groups have been obtained on the basis of synthetic and natural polymers [4][5][6] including polysaccharides [7,8].…”

Surface activity of amphiphilic cationic pH-responsive poly(4-vinylpyridine) microgel at air/water interface

“…This data indicates that the aggregation of p(4-VP) microgels in aqueous solutions is pH dependant. Furthermore, the location of charged moieties at the surface and/or inside the microgel affects the aggregation of microgels at different pH values [46][47][48]. It is expected that when they are located at the surface of the microgel, the pH-dependent ionization will lead to a good interaction of the particles especially at the surface.…”

Heterogeneous Morphology of Random Copolymer Microgels as Reflected in Temperature‐Induced Volume Transition and1H High‐Resolution Transverse Relaxation NMR

“…Our previous results on an amphoteric microgel, obtained by copolymerization of VCL, itaconic acid dimethylester (IADME) and vinylimidazole (VIm), using 1 H highresolution site-selective transverse relaxation NMR also showed a bimodal transverse relaxation behavior indicating a heterogeneous core-corona internal structure. [ 19 ] Efforts were made in order to describe the swelling behavior of microgels using improvements on the Flory's thermodynamic theory for gel systems. [ 20 , 21 ] A combination of the extended Flory-Huggins model [ 22 , 23 ] for mixing solvent and network with a modifi ed Flory-Rehner theory [ 24 ] for elastic contribution was used and fi tted to experimental data obtained for submicron gel particles and bulk gels.…”