Multiple-stimulus-responsive hydrogels of cationic surfactants and azoic salt mixtures

Abstract

New hydrogels having high water content, ∼96 wt%, composed of cationic surfactants, alkyltrimethylammonium bromides (C n TAB, n=12,14,16,and 18), and a small dye molecule, sodium azobzenzene 4,4′-dicarboxylic acid (AzoNa 2 ), was firstly obtained. The three-dimensional network structures of hydrogels were determined by transmission electron microscopy images, scanning electron microscopy images, 1 H nuclear magnetic resonance, and small-angle X-ray scattering measurements. The mechanism of hydrogel formation was also illustrated. The rheological data were obtained to investigate the mechanical strength of hydrogels, which were turned out to be strong mechanical strength (∼10 4 Pa) materials. We found that the strength of the hydrogel depends on the fiber density, which can be controlled by changing the proportion of the two compounds, concentration of surfactants, temperature, and the chain length of the surfactant. Interestingly, the hydrogels were found to have a multiple-stimulus response property. A reversible thermal, UVvis, or a chemical response was investigated in the mixtures of cationic surfactants and azoic salt for the first time. These findings may find potential applications such as sensors, actuators, shape memories, and drug delivery systems, etc.

Supramolecular Hydrogelators and Hydrogels: From Soft Matter to Molecular Biomaterials

“…The authors found that UV irradiation or the addition of a salt and an acid results in a gel–sol transition, while the addition of a base hardly changes the hydrogel, suggesting that it is important to maintain the ionic state of 50 for the hydrogelation. 296 Ward et al reported that amphiphilic guanidinium alkylbenzenesulfonates 51 exhibit lyotropic behavior in aqueous solvents. At a relatively high concentration, 10 wt %, 51 self-assembles to form a lamellar structure and results in hydrogels.…”

“…In a typical example, 49 and 50 in a 2:1 ratio form a hydrogel at a concentration of about 4.0 wt %. The authors found that UV irradiation or the addition of a salt and an acid results in a gel–sol transition, while the addition of a base hardly changes the hydrogel, suggesting that it is important to maintain the ionic state of 50 for the hydrogelation . Ward et al reported that amphiphilic guanidinium alkylbenzenesulfonates 51 exhibit lyotropic behavior in aqueous solvents.…”

Thermoreversible Gel Lubricants through Universal Supramolecular Assembly of a Nonionic Surfactant in a Variety of Base Lubricating Liquids

“…The LMWGs can form random three-dimensional networks and cavities in which liquids (lubricant oils) are trapped through H-bonding, π–π stacking, hydrophobic interaction, van der Waals force, London dispersion forces, and electrostatic interaction. , A variety type of molecules have been used as the LMWGs, for example amino acid, , fatty acid derivatives, quterary ammonium salts, , urea, , anthracene derivatives, organometallic compounds, steroid derivatives, and so on. They can either gelate water or organic solvents and ILs, forming hydrogels, organogels, ionogel, respectively .…”

Amino‐terminated Poly(ethylene glycol) (AT‐PEG) Polymer Hydrogels as Efficient Anionic Dye Adsorbents

“…The rheological property can be evaluated by measuring the viscoelasticity and the mechanical strength of the gels, and which can provide guidelines for gel applications . The solid‐like network structure of gels, when implanted to be sheared under an increasing stress, will break suddenly at a critical shear stress, τ*, beyond which a Newtonian‐like flow occurs .…”