Double-hydrophilic copolymers containing different hydrophilic blocks can self-assemble to form stable vesicles in aqueous solution despite having no apparent hydrophobic block. Self-assembly of double-hydrophilic copolymers consisting of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) is intriguing because not only is PAA responsive to changes in pH, but also PAA can participate in hydrogen bonding interactions with itself or PEO under appropriate pH conditions. We present a class of pH-sensitive polymer vesicles prepared by the self-assembly of double-hydrophilic PEO–PAA diblock copolymers (Scheme 1). To the best of our knowledge, this is the first work that shows the formation of micron-sized vesicles of PEO–PAA copolymers. We survey the self-assembled morphologies of PEO–PAA copolymers with different PEO fractions and demonstrate substantial degradation of giant polymer vesicles by adjusting solution pH. Furthermore, these vesicles are capable of encapsulating and releasing small molecule cargo. Because the switching behavior of the diblock copolymers occurs at biologically-relevant pH environments (2 to 9), these polymer vesicles have potential biomedical applications as smart delivery vehicles.

Self-assembly/disassembly of giant double-hydrophilic polymersomes at biologically-relevant pH

2019 Spring National Meeting

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