Antifreeze and Rheological Properties of Injectable Triblock Copolymer Hydrogels with Supramolecular Junctions

ABC triblock copolymers composed of hydrophobic poly(ε‐caprolactone) (PCL), zwitterionic poly(carboxybetaine methacrylate) midblock, and P(PEGMA‐UPy0.15) containing supramolecular ureidopyrimidinone moieties, poly(ε‐caprolactone‐block‐carboxybetaine methacrylate‐block‐[poly(ethylene glycol) methyl ether methacrylate‐co‐(α‐methacryloyl‐ω‐(6‐(3‐(6‐methyl‐4‐oxo‐1,4‐dihydropyrimidin‐2‐yl)ureido)hexylcarbamoyloxy)poly(ethylene glycol))]), are investigated to achieve multifunctional antifreeze hydrogels. The PCL and P(PEGMA‐UPy0.15) blocks induce the formation of physical network with a hierarchical nanostructure comprising hydrophobic PCL cores and supramolecular junctions, respectively. The super‐hydrophilic nature of polyzwitterion midblocks and the confinement effect of the supramolecular junctions enhance the antifreeze performance, where the majority of water molecules remains supercooled below sub‐zero temperature. The hydrogel relaxation characterized over a wide range of timescale reveals that the facile dynamics of the supramolecular junctions lead to the self‐healing and injectability of the hydrogels. In conjunction with the biodegradable PCL cores, the antifreeze and rheological characteristics of the triblock copolymer hydrogels provide significant potential to use for cryo‐preservable and bio‐injectable drug storage and delivery. Triblock copolymer hydrogels containing supramolecular associative units are investigated for their intriguing and useful properties, including outstanding antifreeze performance, facile recovery after break‐down (self‐healing), and shear‐thinning property. The integration of such characteristics into a single system highlights the applicability of this system as cryo‐preservable injectable hydrogels for controlled drug delivery and many other fields.