Reversible Hydrogels with Switchable Diffusive Permeability

Abstract

Hydrogels are polymer networks swollen in water that are characterized by soft mechanics and high permeability. This makes them good candidates for separation and membrane technologies. The diffusion is controlled by the mesh size of the network, and this can be made tunable through the introduction of thermoresponsive polymers. However, this is still a developing field. To contribute to this development, a dual dynamic network is formed composed of four‐arm polyethylene glycol precursors in which each arm is functionalized with both a terpyridine moiety capable of forming reversible metal–ligand complexes along with branches of poly(N‐isopropylacrylamide) (pNIPAAm), which can be switched between expanded and collapsed states and therewith offers a path for switching the microscopic gel‐network mesh size, along with the macroscopic gel elasticity. The dually sensitive hydrogel has the capability of doubling its elastic modulus when going above the lower critical solution temperature (LCST) of pNIPAAm. In addition, the diffusive permeability of the hydrogel is switched upon change of temperature, whereby diffusants are trapped above the LCST of pNIPAAm. Moreover, it is possible to disassemble and reform the gel upon change of pH. With that, the hydrogel has potential application as a switchable and reversible membrane.

Defect-controlled softness, diffusive permeability, and mesh-topology of metallo-supramolecular hydrogels

“…Since this is the system with the highest modulus, it will be further taken as reference when compared to the other samples. If the plateau modulus is considered as a quantification of the elastically active network strands, 5 the continuous decrease of G p depending on an increasing amount of 8-arm in the networks, indicates a decreasing degree of network connectivity. As the matter of fact, with a higher density of arms per each molecule, the 8-arm is more likely to form intra-molecular instead of inter-molecular associations.…”

“…Prominent examples for inhomogeneities are found in hydrogels, which are three-dimensional polymer networks swollen in water. 5–7 These polymer networks can be formed by connection of polymer strands either by supramolecular or covalent crosslinks. While covalent networks are stable in form and shape, supramolecular networks have the great advantage of being dynamic which means being responsive and recyclable.…”

“…18 In an own previous work, we introduced poly( N -isopropylacrylamide) (pNIPAAm) dangling chains into a supramolecular polymer network and were able to similarly hinder the diffusion of small probes upon switching temperature above the lower critical solution temperature of pNIPAAm. 5 Similarly, we investigated how the network dynamics of gels, constituted by chains carrying sticky side-groups, changes with the introduction of sticky tracers having the same or lower connectivity than the network itself, thereby creating local connectivity defects. 4 Our findings show that the chain dynamics is enhanced in case of the network with connectivity defects, meaning that the probe diffuses faster than expected.…”

Understanding Matrix Stiffness in Vinyl Polymer Hydrogels: Implications in Bone Tissue Engineering

“…The decreased swelling behavior (Figure c­(i),(ii)) of mineral-induced hydrogels after a certain duration is due to intense contacts between organic and inorganic phases as well as possible moderate interactions between vinyl groups. These extensive connections produce compact hydrogels with lower media diffusion into the hydrogel network, which alters their swelling behavior . The 3D scaffold breakdown behavior is complex in a dynamic physiological microenvironment and can vary greatly between systems.…”

Simulated Investigation in Wormhole Expansion Law of Gelling Acid Etching and Its Influencing Factors in Deep Carbonate Reservoirs

“…Research on gelling acid for reservoir stimulation has focused on middle and deep carbonate reservoirs and other areas [ 27 , 28 , 29 , 30 ]. Yuman Wu et al (2022) [ 31 ] proposed a betaine-based gel used for hydraulic fracturing, it was proved that KCl improves the temperature resistance and increases the viscosity of the optimized fracturing fluid, and the viscoelastic surfactant gel had high shear resistance and high sand-carrying performance.…”