Multiresponsive Azobenzene-Modified Microgels with Polyampholyte Behavior

Multiresponsivemicrogels that are able to respond to differentstimuli are essential for the development of complex soft matter systems.Here, light, temperature, and pH-multiresponsive microgels were successfullyfabricated via mAzo post-modification on the prepared poly(N-vinylcaprolactam-co-acrylic acid) microgels.The synthesized mAzo-modified microgels exhibit reversible photoswitchingbehavior upon blue, green or red light irradiation, and light triggerssize change, as a result of the trans-cis isomerization inducedby different visible light irradiations. The synthesized microgelsalso exhibit temperature responsiveness reflected by the temperature-inducedchange of hydrodynamic radius, and the incorporated hydrophobic mAzounits contribute to shifts to lower values of the volume phase transitiontemperature (VPTT) of the microgels. Importantly, the mAzo-modifiedmicrogels demonstrate a charge reversal behavior, and a "V"-shapedtrend of size change from pH 4 to pH 10 was obtained because of theexistence of mAzo moieties and carboxyl groups in the microgels.