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Injectable, Self-Healing, and Multi-Responsive Hydrogels via Dynamic Covalent Bond Formation between Benzoxaborole and Hydroxyl Groups

Chen, Yangjun, Tan, Zhengzhong, Wang, Wenda, Peng, Yi-Yang, Narain, Ravin
Biomacromolecules 2018 v.20 no.2 pp. 1028-1035
chemical bonding, composite polymers, esters, galactose, hydrogels, hydrophilicity, mechanical properties, mixing, moieties, pH, polymerization, temperature
Hydrogels that are injectable, self-healing, and multiresponsive are becoming increasingly relevant for a wide range of applications. In this work, we have successfully developed a novel approach in the fabrication of smart hydrogels with all the above properties. A symmetrical ABA triblock copolymer was first synthesized via atom transfer radical polymerization with a temperature responsive middle block and two permanently hydrophilic glycopolymer chains on both ends. Hydrogels were subsequently constructed by mixing the triblock copolymer with another linear hydrophilic copolymer bearing benzoxaborole groups. The interactions of the benzoxaborole groups with the sugar hydroxyl groups allowed the formation of dynamic covalent bonds. The resulting hydrogels exhibited temperature, pH, and sugar responsiveness. Rheological studies confirmed that the mechanical property can be tuned by changing the pH as well as the galactose/benzoxaborole molar ratio. Furthermore, the hydrogels showed excellent self-healing ability and shear-thinning performance due to the inherent well-known dynamic covalent bonds of boronic esters. Therefore, these types of hydrogels can have excellent biomedical applications.