Micelle‐crosslinked hydrogels with stretchable, self‐healing, and selectively adhesive properties: Random copolymers work as dynamic yet self‐sorting domains

Abstract

The design of crosslinking domains is a vital factor to create functional hydrogels with controlled physical, mechanical, and adhesive properties. This paper demonstrates versatile synthetic systems of micelle-crosslinked hydrogels with highly stretchable, self-healing, and selectively adhesive properties. For this, methacrylate-bearing random copolymer micelles are designed as physical and covalent crosslink domains via the self-assembly of amphiphilic random copolymers carrying hydrophilic poly(ethylene glycol) (PEG), hydrophobic butyl or dodecyl groups, and methacrylate-terminal PEG in water. The size, aggregation number, and pendant methacrylate number of the micelles are controlled by the composition and degree of polymerization. Hydrogels are efficiently obtained from the free radical polymerization of hydrophilic monomers such as PEG acrylate and acrylamide in the presence of the micelle crosslinkers in water. Owing to the dynamic yet selective chain exchange properties of the micelle domains, the hydrogels are highly stretchable up to over 1000% and show self-healing and selectively adhesive properties. The self-healing of hydrogels is promoted upon heating due to the fast chain exchange of the micelle domains, whereas hydrogels consisting of micelles with different alkyl groups are never adhesive because of their self-sorting properties.