Manipulation of block copolymer vesicles using CO2: dissociation or “breathing”

Abstract

We demonstrate a general way to prepare CO2-responsive block copolymer (BCP) vesicles by employing poly(N,N′-diethylaminoethylmethacrylate) (PDEAEMA) as the hydrophobic block. Two amphiphilic BCPs containing either poly(N,N′-dimethylacrylamide) (PDMA) or poly(ethylene oxide) (PEO) as the hydrophilic block and either PDEAEMA or P(DEAEMA-co-CMA) (photo-cross-linkable PDEAEMA containing a number of coumarin side groups) as the hydrophobic block were synthesized and used to prepare vesicles in aqueous solutions. These vesicles exhibit very good responsiveness to gas stimuli. On the one hand, upon CO2 bubbling, PDMA-b-PDEAEMA vesicles display morphological changes that range from expansion to complete dissociation, which is thought to be determined by the protonation degree of the DEAEMA unit in the vesicle membrane. On the other hand, PEO-b-P(DEAEMA-co-CMA) vesicles whose membrane is cross-linked through coumarin dimerization can undergo reversible expansion and contraction under alternating passage of CO2 and argon (Ar) in solution; the extent of such vesicle “breathing” can be controlled by adjusting the degree of dimerization of coumarin within the vesicle membrane. Finally, pyrene-1,3,6,8-tetrasulfonic acid tetrasodium was used as a model drug, allowing its CO2-controllable release from these two vesicle types to be investigated.