Thermoresponsive Dendronized Microgels through In Situ Cross-Linking Polymerization to Exhibit Enhanced Confinement for Solvatochromic Dyes

Polymeric microgels form a classof promising materials for variousapplications based on their highly tunable swelling and cooperativeinteractions between the cross-linked polymer chains. Here, we reporton a convenient route for the fabrication of polymeric microgels through in situ cross-linking polymerization of thermally collapsedmacromonomers carrying 3-fold dendritic oligoethylene glycol (OEG)pendants, affording thermoresponsive dendronized microgels with intriguingmicroconfinement. This methodology has been proven to be versatileand can be used to prepare intelligent microgels through homopolymerizationof thermoresponsive dendronized macromonomers, or via copolymerization with either hydrophobic or hydrophilic, and dendronizedor nondendronized comonomers. The thermoresponsive microgels of uniformsizes undergo shrinking or swelling by changing the temperature aboveor below their phase transition temperatures and thus exhibit tunablemicroconfinement to encapsulated solvatochromic dye molecules. Thisoutstanding capacity for confinement by the microgels is comparedto linear copolymers with or without dendritic architectures and isproposed to originate from both dendritic crowding effects and cooperativeinteractions between polymer chains within the network. This remarkablefeature of microconfinement opens a new era for microgels to reversiblyencapsulate and protect guest molecules and provides a platform tomanipulate the functions of the encapsulated guests through externalstimuli.