Magnetically tunable viscoelastic response of soft magnetic nanocomposites with wormlike surfactant micellar matrix

Abstract

Magnetorheological effects in viscoelastic soft magnetic nanocomposites (SMNs) composed of submicron magnetite particles embedded in a network of wormlike micelles (WLMs) of surfactant were studied in a homogeneous magnetic field. In field, the SMNs showed rapid rise of storage and loss moduli by a few orders of magnitude as a result of the ordering of magnetized particles into chain-like or columnar structures.Moreover, solid-like behavior and yield stress of the SMNs were observed. Study of rheological response on periodic switching of field revealed that the initial viscoelasticity of SMNs did not recover completely after removing field, which was attributed to extremely long relaxation time of the WLM network. It was found that the variation of storage and moduli loss was associated with the stepwise change in magnetic field; this can be fitted by two-exponential functions, a characteristic time for the slower process being almost the same as the relaxation time of SMN without field, indicating that this process is essentially determined by the viscoelastic properties of the matrix.

Review on Enhancing Rheological Characteristics of Viscoelastic Surfactant Fracturing Fluids by Nanoparticles: Advances, Challenges, and Perspectives

“…Very small nanoparticles around 3 nm in diameter were shown to have no effect on viscosity in WLM solutions, though they incorporate into micellar chains as pearl-necklace structures. 49 Meanwhile, for anionic WLMs of sodium oleate and octyl trimethylammonium bromide mixed with negatively charged silica, zero-shear viscosity increased 5-fold when particle size decreased from 60 to 15 nm. Clearly particle size impacts pseudo-cross-linking and rheology, but the mechanisms at different dimensions are not yet fully characterized.…”

Injectable ultra-soft hydrogel with natural nanoclay

“…7(a), it is seen that the disruption of the network is faster than the recovery. Gradual growth of the storage modulus takes tens of the seconds that is close to the typical relaxation time for the WLM networks [20,25]. Such restoring rate is comparable to the restoring rate of various injectable systems for wound healing application [5].…”

“…Properties of the WLM network can be modified by nanoparticles. Until now, only spherical inorganic particles were dispersed within WLM network [14][15][16][17][18][19][20]. It was shown that these particles can significantly increase the rheological properties.…”

“…In addition to silica nanoparticles, some functional nanoparticles were incorporated into WLM networks including pyroelectric [16] and magnetic particles [17,19,20]. Introduction of pyroelectric particles made the hydrogel sensitive to temperature variation.…”

“…Heating increased the charge on the surface of particles thereby strengthening their interaction with oppositely charged surfactant micelles and enhancing the rheological properties [16]. In their turn, magnetic particles imparted magnetoresponsive properties to WLM hydrogel [17,19,20]. The aggregation of particles into chain-like/column structures because of magnetization resulted in a solid-like behavior even in rather low magnetic fields and at small volume fraction of particles, indicating the weak restrictions imposed by the matrix on the reorganization of particles in the field, which can be due to the self-assembled structure of the micellar network [19].…”