To face the increasing demand of self-healing hydrogels with biocompatibility and high performances, a new class of cellulose-based self-healing hydrogels are constructed through dynamic covalent acylhydrazone linkages. The carboxyethyl cellulose-graft-dithiodipropionate dihydrazide and dibenzaldehyde-terminated poly(ethylene glycol) are synthesized, and then the hydrogels are formed from their mixed solutions under 4-amino-DL-phenylalanine (4a-Phe) catalysis. The chemical structure, as well as microscopic morphologies, gelation times, mechanical and self-healing performances of the hydrogels are investigated with 1 H NMR, Fourier transform infrared spectroscopy, atomic force microscopy, rheological and compression measurements. Their gelation times can be controlled by varying the total polymer concentration or 4a-Phe content. The resulted hydrogels exhibit excellent self-healing ability with a high healing efficiency (≈96%) and good mechanical properties. Moreover, the hydrogels display pH/redox dual responsive sol-gel transition behaviors, and are applied successfully to the controlled release of doxorubicin. Importantly, benefitting from the excellent biocompatibility and the reversibly cross-linked networks, the hydrogels can function as suitable 3D culture scaffolds for L929 cells, leading to the encapsulated cells maintaining a high viability and proliferative capacity. Therefore, the cellulose-based self-healing hydrogels show potential applications in drug delivery and 3D cell culture for tissue engineering.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201703174.For this purpose, intensive efforts have been made so far to design and fabricate self-healing hydrogels by incorporating dynamic covalent and noncovalent bonds into the hydrogel networks. [2] Since dynamic covalent bonds, such as Schiff bases, [3] disulfide bonds, [4] Diels-Alder reactions, [5] and phenylboronate complexations, [6] can integrate both the stability of covalent bonds and the reversibility of noncovalent bonds, [2a] they have been employed to prepare the self-healing hydrogels with diverse functions. In particular, chitosan-based self-healing hydrogels constructed via Schiff bases have been widely explored as biomaterials for hemostasis, [7] drug delivery, [8] cell therapy, and 3D cell culture, [3a,9] due to their good biocompatibility and automatic repair ability under physiological conditions. [3b] However, the relatively fast hydrolytic degradation rate, [2a] poor structural integrity, and weak mechanical properties [3b] of those hydrogels impede their biomedical applications for achieving longer-lasting functions. Acylhydrazone bonds, which formed via the condensation of hydrazides with carbonyl groups, are very close relatives to Schiff bases, but are much more stable. Thus, the acylhydrazone bonds have been utilized to construct the selfhealing hydrogels with robust mechanical properties. [4b,10] For instance, a strong self-healing hydrogel that...
Responsive polymer interfacial materials are ideal candidates for controlling surface wetting behavior. Here we developed smart nanostructured electrospun polymer membranes which are capable of switching oil/water wettability using CO2 as the trigger. In particular, the combination of CO2 -responsiveness and porous nanostructure enables the as-prepared membranes to be used as a novel oil/water on-off switch. We anticipate that the promising versatility and simplicity of this system would not only open up a new way of surface wettability change regulation by gas, but also have obvious advantages in terms of highly controlled oil/water separation and CO2 applications.
Electrochemical stimuli have attracted much attention in recent years as they are simple, clean and can be widely applied in biological systems and material science. As one type of common guest molecules, ferrocene and its derivatives have been well studied with different host molecules, mainly including cyclodextrins, cucurbiturils, pillararenes and calixarenes. This article generally summarizes the recent work on the host-guest interactions between ferrocene derivatives and their host molecules, as well as various supramolecular systems based on these interactions. In addition, the development and outlook of electrochemical responsive systems are also discussed.
A one-step synthesis of nanotubes by RAFT dispersion polymerization of cyclodextrin/styrene (CD/St) complexes directly in water is presented. The resulted amphiphilic PEG-b-PS diblock copolymers self-assemble in situ into nanoparticles with various morphologies. Spheres, worms, lamellae, and nanotubes were controllably obtained. Because of the complexation, the swelling degree of polystyrene (PS) blocks by free St is limited, resulting in limited mobility of PS chains. Consequently, kinetically trapped lamellae and nanotubes were obtained instead of spherical vesicles. During the formation of nanotubes, small vesicles first formed at the ends of the tape-like lamellae, then grew and fused into nanotubes with a limited chain rearrangement. The introduction of a host-guest interaction based on CDs enables the aqueous dispersion polymerization of water-immiscible monomers, and produces kinetically trapped nanostructures, which could be a powerful technique for nanomaterials synthesis.
A series of azo-containing copolymeric assemblies based on poly( N , N -dimethylaminoethyl methacrylate)-b-poly[(benzyl methacrylate)-co-(4-phenylazophenyl methacrylate)] [PDMA-b-P(BzMA-co-AzoMA)] were prepared by reversible addition–fragmentation chain transfer polymerization-induced self-assembly at high solid contents. Depending on the chain length of P(BzMA-co-AzoMA), spheres, worms, and vesicles were readily prepared. These azo-containing wormlike micelles underwent reversible worm-to-vesicle transformation upon alternative UV/vis light irradiation. By investigating the morphology evolution, a series of intermediates were observed, including coalesced worms as well as “octopus”-like and “jellyfish”-like structures. The morphology transformation was rationalized by the volume change of the P(BzMA-co-AzoMA) block caused by the trans–cis isomerization of the azobenzene groups. It is the first demonstration of light-stimulated reversible worm-to-vesicle transition and would benefit for the understanding of morphology evolution of polymer assemblies under external stimuli.
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