Electrostatic interaction is strong but usually diminishes in high ionic-strength environments. Biosystems can use this interaction through adjacent cationic–aromatic amino acids sequence of proteins even in a saline medium. Application of such specific sequence to the development of cationic polymer materials adhesive to negatively charged surfaces in saline environments is challenging due to the difficulty in controlling the copolymer sequences. Here, we discover that copolymers with adjacent cation–aromatic sequences can be synthesized through cation–π complex-aided free-radical polymerization. Sequence controlled hydrogels from diverse cation/aromatic monomers exhibit fast, strong but reversible adhesion to negatively charged surfaces in seawater. Aromatics on copolymers are found to enhance the electrostatic interactions of their adjacent cationic residues to the counter surfaces, even in a high ionic-strength medium that screens the electrostatic interaction for common polyelectrolytes. This work opens a pathway to develop adhesives using saline water.
We report here a zwitterionic copolymer based non-covalently cross-linked hydrogel with intrinsic self-healing nature for potential use in enhanced oil recovery.
We report a multi-stimuli responsive supramolecular hydrogel with great potential for biomedical application, which was composed of the micelle-forming diblock copolymer and physically cross-linked by complexation between ferric ions and carboxylic acid groups, exhibiting gel–sol transition caused by UV irradiation, multidentate ligands (EDTA) and redox agents (Na2S2O4).
Inspired by the toughening mechanism of double-network (DN) gels, tough hydrogel composites with a sandwich structure were fabricated from photoresponsive polymers. By copolymerization of hydrophilic monomers, 2ureidoethyl methacrylate (UM), and photoresponsive hydrophobic monomers, (2-nitrobenzyloxycarbonylaminoethyl methacrylate (NBOC)) at high concentrations, physical hydrogels that are soft and highly stretchable are formed due to the hydrophobic associations of NBOC, serving as dynamic crosslinkers. By UV irradiation, the physical crosslinking switches into chemical crosslinking, and the soft physical hydrogels transform into rigid and less stretchable chemical hydrogels. By UV curing the surface layers of the physical hydrogels, we prepared hydrogel composites having a sandwiched structure with two rigid outer layers and a soft inner layer. The molecular-level continuous interfaces and matched swelling ratios between the layers ensure the macroscale hydrogel composites' high strength and toughness with a DN gel effect. The outer layers fracture preferentially at deformation, playing a role like the first network of a DN gel, while the inner layer maintains the integrity, playing a role resembling the second network. The evolution of the fracture morphology of the rigid layers gives useful insight into the internal fracture process of DN gels.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.