CO2-sensitive amphiphilic triblock copolymer self-assembly morphology transition and accelerating drug release from polymeric vesicle

A series of triblock copolymers, containing a CO 2 -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 pH and conductivity tests showed that the triblock copolymer exhibited switchable responsiveness to CO 2 , i.e. a relatively low conductivity of solution could be switched on and off by bubbling and removing of CO 2 , and the triblock copolymer aqueous solution displayed a CO 2 -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 CO 2 stimuli showed the potential application in drug delivery domains; after CO 2 bubbling, the drug release rate could be accelerated. Finally, reasonable mechanism of CO 2 -switchable morphology changes and CO 2 -induced drug release was proposed.