CO2-sensitive Amphiphilic Triblock Copolymer Self-assembly Morphology Transition and Accelerating Drug Release from Polymeric Vesicle

A series of triblock copolymers, containing a CO2-switchable block poly（2-（dimethylamino）ethyl methacrylate）（PDM） block and two symmetrical hydrophilic blocks polyacrylamide（PAM）, were synthesized using atom transfer radical polymerization（ATRP） method. The p H and conductivity tests showed that the triblock copolymer exhibited switchable responsiveness to CO2, i.e. a relatively low conductivity of solution could be switched on and off by bubbling and removing of CO2, and the triblock copolymer aqueous solution displayed a CO2-switchable viscosity variation. The changes were all attributed to protonation of tertiary amine groups in PDM blocks and proven by 1 H-NMR. Cryogenic transmission electron microscopy and dynamic light scattering characterization demonstrated that the viscosity variation was the result of a unilamellar vesicle-network aggregate structure transition. The release of rhodamine B from the vesicles with and without CO2 stimuli showed the potential application in drug delivery domains; after CO2 bubbling, the drug release rate could be accelerated. Finally, reasonable mechanism of CO2-switchable morphology changes and CO2-induced drug release was proposed.