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CO2 Stimuli-Responsive, Injectable Block Copolymer Hydrogels Cross-Linked by Discrete Organoplatinum(II) Metallacycles via Stepwise Post-Assembly Polymerization

Zheng, Wei, Yang, Guang, Shao, Nannan, Chen, Li-Jun, Ou, Bo, Jiang, Shu-Ting, Chen, Guosong, Yang, Hai-Bo
Journal of the American Chemical Society 2017 v.139 no.39 pp. 13811-13820
biocompatibility, carbon dioxide, composite polymers, crosslinking, hydrogels, polymerization, temperature
Supramolecular polymeric gels cross-linked by well-defined, discrete metal–organic macrocycles (MOMs) or metal–organic cages have become a prevailing topic within the field of supramolecular self-assembly. However, the realization of supramolecular polymeric hydrogels cross-linked by discrete organometallic architectures with good biocompatibility is still a great challenge. Herein, we present the successful preparation of CO₂ stimuli-responsive, injectable block copolymer hydrogels cross-linked by discrete organoplatinum(II) metallacycles. Through the combination of coordination-driven self-assembly and stepwise post-assembly polymerization, star block copolymers (SBCPs) containing well-defined hexagonal metallacycles as cores were successfully prepared, which featured CO₂ stimuli-responsive properties including CO₂-triggered morphology transition and CO₂-induced thermoresponsive behavior. Interestingly, the resultant SBCPs were capable of forming supramolecular hydrogels with MOMs as junctions near physiological temperature, which allowed the realization of a reversible gel-to-sol transformation through the removal and addition of CO₂. More importantly, the resultant supramolecular hydrogels presented good cytocompatibility in vitro. Therefore, this study provides a new strategy for the construction of new “smart” supramolecular hydrogels with promising applications as biological materials.