Synthesis, self-assembly and drug release behaviors of pH-responsive copolymers ethyl cellulose-graft-PDEAEMA through ATRP

The pH-responsive ethyl cellulose graft poly(2-(diethylamino) ethyl methacrylate) (EC-g-PDEAEMA) copolymers were synthesized through atom transfer radical polymerization (ATRP). Kinetic analysis confirmed the reaction is living and controllable. The graft copolymers can form micelles in acid aqueous medium. The critical micelle concentration (CMC) of the graft copolymers decreases with the increase of the graft length and graft density. The resultant micelles show the pH-sensitivity. The decrease in the hydrodynamic radius of the micelles at pH 6-6.9 attributes to collapse of the side PDEAEMA chains in the shell of the micelles due to the deprotonation, which was further confirmed by TEM observation. The loading and controlled release of drugs in the micelles was investigated by using rifampicin (RIF) as the model drug. It was found that the cumulant release of RIF in the buffer solution at pH 6.6 is higher than that at pH 7.4.