Characterization of Temperature-Responsive Graft Copolymer with Polycarbonate Oligo Segment

Abstract

Graft copolymers with temperature-responsive units were designed and synthesized using a macromonomer method. A hydrophilic monomer was copolymerized with a macromonomer with a hydrophobic oligo segment. The copolymer spontaneously formed polymer colloids by intermolecular interactions in aqueous solutions. The copolymers were analyzed by UV-Vis spectroscopy, dynamic light scattering, and a fluorescence probe technique under different temperatures. The particle size of the copolymer colloids ranged from 20 to 60 nm at 25°C and larger aggregates were observed at higher temperatures. Increasing the hydrophilic N-hydroxyethyl acrylamide monomer units in the copolymer was induced by decreasing of lower critical solution temperature along with polymeric aggregation. The molecular incorporation of the copolymer was estimated using pyrene as a fluorescence probe, and the change in critical association concentration (CAC) was estimated. The CAC values for the copolymers with hydrophobic segments were estimated to be between 3.0 ! 10 -2 and 4.0 ! 10 -2 mg/mL. In addition, the copolymers formed stable colloids in aqueous media.