ROMP Synthesis of Side‐Chain Ferrocene‐Containing Polyelectrolyte and Its Redox‐Responsive Hydrogels Showing Dramatically Improved Swelling with β‐Cyclodextrin

Abstract

A new side‐chain ferrocene (Fc)‐containing polyelectrolyte has been synthesized by controlled ring‐opening metathesis polymerization of a water‐soluble Fc‐containing norbornene‐based quaternary ammonium salt, as well as the corresponding covalently cross‐linked polyelectrolyte hydrogel. In order to provide Fc‐containing supramolecular polyelectrolyte hydrogels whose swelling property is largely improved by host−guest interaction, a covalently cross‐linked polyelectrolyte hydrogel is soaked into the β‐CD aqueous solution to form β‐CD@Fc supramolecular polyelectrolyte hydrogel, or alternatively the quaternary ammonium salt supramolecular monomer is first formed, then copolymerized with a crosslinking agent to fabricate the supramolecular hydrogel with better water absorption ability. All the Fc‐containing hydrogels exhibited good redox‐responsiveness with swelling–shrinking behaviors by chemically reversibly adjusting the disassembly/assembly of β‐CD@Fc inclusion complexes. This is the first example of side‐chain Fc‐containing polycationic supramolecular hydrogels possessing swelling–shrinking properties based on the splitting/combining of β‐CD and Fc units, and potential applications are expected as controlled drug delivery and actuators.

An injectable and self-healing hydrogel with dual physical crosslinking for in-situ bone formation

“…Compared to previous studies [ [27] , [28] ], this self-healing property of our CMS hydrogel was also satisfactory. We believe that this efficient self-healing property of CMS hydrogel guarantees its long-term integrality after in-situ implantation into the bone defects [ [29] , [30] , [31] , [32] , [33] ]. At the same time, the reversible physical crosslinks of CMS hydrogel also endowed it with an injectable property.…”

Recent Advances in Host‐Guest Supramolecular Hydrogels for Biomedical Applications

“…β ‐CD/adamantine crosslinks may display a certain extent of thermal‐responsiveness due to the tendency to break apart at high temperatures. The ferrocene/CD complexes may respond to oxidation due to the hydrophobic to hydrophilic transition of ferrocene during the oxidation process [17,18] …”

“…The ferrocene/CD complexes may respond to oxidation due to the hydrophobic to hydrophilic transition of ferrocene during the oxidation process. [17,18] The formation of polyrotaxanes or poly(pseudo)rotaxanes is the other approach to produce hydrogels through host-guest interactions (Figure 1b). In addition to binding with small molecule guest motifs, macrocyclic hosts can also be threaded onto polymer chains with bulky end-capping groups (referred to as "polyrotaxanes") or without end-caps (referred to as "poly(pseudo)rotaxanes"), giving rise to a necklace-like supramolecular structure.…”

Tough, Self-Adhesive, Antibacterial, and Recyclable Supramolecular Double Network Flexible Hydrogel Sensor Based on PVA/Chitosan/Cyclodextrin

“…CDs can be used as the host molecules to selectively package various guest molecules [e.g., ferrocene (Fc), azobenzene, adamantane, and so forth.] to form reversible dynamic cross-linking and make hydrogels have certain fatigue resistance and self-recovery ability. − For example, Harada et al prepared hydrogels based on the host–guest interaction of β-CD and Fc with good self-recovery performance . In addition, dynamic covalent bonds or reversible chemical reactions (e.g., Schiff base bond, borate bond, disulfide bond, and so forth.)…”