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

Abstract

Polymeric microgels form a class of promising materials for various applications based on their highly tunable swelling and cooperative interactions between the cross-linked polymer chains. Here, we report on a convenient route for the fabrication of polymeric microgels through in situ cross-linking polymerization of thermally collapsed macromonomers carrying 3-fold dendritic oligoethylene glycol (OEG) pendants, affording thermoresponsive dendronized microgels with intriguing microconfinement. This methodology has been proven to be versatile and can be used to prepare intelligent microgels through homopolymerization of thermoresponsive dendronized macromonomers, or via copolymerization with either hydrophobic or hydrophilic, and dendronized or nondendronized comonomers. The thermoresponsive microgels of uniform sizes undergo shrinking or swelling by changing the temperature above or below their phase transition temperatures and thus exhibit tunable microconfinement to encapsulated solvatochromic dye molecules. This outstanding capacity for confinement by the microgels is compared to linear copolymers with or without dendritic architectures and is proposed to originate from both dendritic crowding effects and cooperative interactions between polymer chains within the network. This remarkable feature of microconfinement opens a new era for microgels to reversibly encapsulate and protect guest molecules and provides a platform to manipulate the functions of the encapsulated guests through external stimuli.