Polyglycidol-Based Prepolymers to Tune the Nanostructure of Microgels

The use of prepolymers for microgel synthesis via miniemulsification allows predefining the chemical functionality and the nanostructure of microgels. We report on tailor-made polyglycidol-based prepolymers using three protected glycidol monomers (allyl glycidyl ether, AGE; ethoxy ethyl glycidyl ether, EEGE; and tert-butyl glycidyl ether, tBGE). AGE with its pendant double bonds serves as site for cross-linking or functionalization, whereas the EEGE and tBGE building blocks represent precursors for hydroxyl functionalities. Following the prepolymer approach, we design statistical and block copolymers to control the nanostructure of the microgel. Cross-linking of the prepolymers is achieved in miniemulsions under UV irradiation in a thiol-ene click type reaction addressing the allyl groups with 2,2'(ethylenedioxy)diethanethiol. Analysis with cryo-TEM reveals that microgels derived from poly(glycidol)-block-poly(AGE) show larger hydrophobic domains than microgels derived from statistical copolymers. Additionally, the cross-linking of pH responsive tBGE/AGE prepolymers with different microstructures leads to microgels with nanostructures differing in local charge distributions.