Article pubs.acs.org/Macromolecules
Cite This: Macromolecules XXXX, XXX, XXX−XXX
pH- and Reductant-Responsive Polymeric Vesicles with Robust Membrane-Cross-Linked Structures: In Situ Cross-Linking in Polymerization-Induced Self-Assembly Miao Chen, Jia-Wei Li, Wen-Jian Zhang,* Chun-Yan Hong,* and Cai-Yuan Pan Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
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ABSTRACT: Polymerization-induced self-assembly (PISA) has been established as a powerful strategy for fabrication of polymeric nanoobjects in the past decade. However, in comparison with the traditional self-assembly method, PISA is unsatisfactory in preparation of vesicles with chemical versatility of membrane-forming block for tunable membrane properties, which limits the further application of PISAbased vesicles. Besides the stimuli-responsive property, structural integrity of the vesicles is another important concern for material applications. In situ cross-linking in PISA via copolymerization with multivinyl comonomers (cross-linkers) seems to be a straightforward and convenient method to afford stabilized nano-objects. However, it is hard to fabricate vesicles with cross-linked membrane via in situ cross-linking strategy because cross-linking greatly limits chain mobility of the produced copolymers and thus prevents morphology transition to form vesicles. In this article, in situ cross-linking in PISA for fabrication of pH- and reductant-responsive vesicles with robust cross-linked structure is realized via RAFT dispersion copolymerization of 2-(diisopropylamino)ethyl methacrylate (DIPEMA) and cystaminebismethacrylamide (CBMA). The cross-linking process is delayed to the late stage of polymerization after the formation of vesicles due to the lower reactivity of the cross-linker CBMA in comparison to the monomer DIPEMA, which is supported by nuclear magnetic resonance (NMR), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The vesicles exhibit dual stimuli-responsive (pH and reductant) release of cargoes. The pH-regulated membrane permeability of the vesicles is due to the pH-responsive hydrophobic-to-hydrophilic transitions of the membrane-forming blocks. Reductantresponsive disaggregation of the vesicles is induced by cleavage of the disulfide linkages in the presence of DL-dithiothreitol (DTT) in acidic aqueous solution. synthesized first and then self-assemble in high dilution (typically
