PEG-Based Microgels Formed by Visible-Light-Mediated Thiol-Ene Photo-Click Reactions.

Step-growth PEG-based microgels are produced via three liquid-liquid two-phase suspension polymerization systems: i) hexane with surfactants Span80/Tween80; ii) mineral oil with surfactant Pluronic F-68; and iii) surfactant-free dextran-rich aqueous solution. Following short vortexing to create monomer droplets, microgels are polymerized by a visible-light-initiated thiol-ene photo-click reaction using eosin-Y as the only photoinitiator. The use of hexane as the organic phase and Span-80/Tween-80 as the surfactants leads to PEG microgels with entrapped solvent droplets that dissolve rapidly with time. Microgels polymerized in mineral oil with surfactant Pluronic F-68 contain no entrapped droplets and are more uniform with smaller sizes. Visible-light-cured step-growth thiol-ene microgels can also be photo­polymerized in a surfactant-free aqueous two-phase system. The sizes of the microgels formed in aqueous phase are one order of magnitude smaller than those formed in organic solvent. Dual-layer microgels are also prepared using two-step thiol-ene reactions. [ABSTRACT FROM AUTHOR]