Viscoelasticity of Graphite Oxide-Based Suspensions in PDMS

Abstract

International audienceThe visco elastic behavior of graphite oxide-loaded PDMS suspensions showed, at low frequencies, a dominant elastic behavior with the appearance of a secondary plateau above 1.5 wt %. Within the investigated concentrations, such behavior was not observed for the graphite and functionalized graphite oxide/PDMS suspensions. This low percolation threshold of GO sheets was attributed to a macroscale aggregation. Furthermore, the critical strain (transition between the linear and nonlinear regime) was observed to slightly s. depend on the particle concentration (gamma(c) proportional to phi(-1 +/- 0.2)) Consequently, the exponent x (x = 0.4), related to the filler volume fraction and the aggregate structure, is lower than 1. This result means that a fractal structure cannot be associated with the aggregation of GO sheets. Actually, GO sheets aggregate into agglomerates that span through the gap between the plates of the rheometer. Agglomeration of GO sheets without any fractal structure explains this particular behavior. Furthermore, recovery tests consisting of subsequent strain sweep tests proved that the initial equilibrium network can be totally and rapidly restored. This particular behavior originates from the low viscosity of the PDMS suspension allowing Brownian motion of graphene oxide sheets to occur within only a few seconds

Functionalization of graphene using deep eutectic solvents

“…This agreed with the findings of a previous study that used the same type of graphene [63]. After mild oxidation with KMnO4, a prominent diffraction peak appeared at 2θ = 11.16°, reflecting the interlayer spacing of 0.79 nm (according to Bragg's law [64,65]). The small peak at 2θ = ~26° suggests the existence of unoxidized graphene [66].…”

Brownian dynamics simulations of nanosheet solutions under shear

“…For W i > 1, intrinsic viscosity only slightly decreases with increasing W i; these results are similar to recently published experimental data on dilute solutions of graphene oxide 36 and graphite oxide suspensions in polydimethylsiloxane (PDMS). 37 Tesfai et al 36 showed that the exponent of the power law relationship between relative viscosity and Wi is within −0.1 to −0.5 while our Figure 9 shows an exponent of ∼−0.25. This also indicates the larger W i value used in Figure 8 yields experimentally relevant viscosity values.…”

Relationship between structures and rheological properties of plate-like particle suspensions

“…In previous work, there are different mechanisms for the shear thinning of nanoparticle suspensions and composites [35][36][37], for instance the shear induced aggregation and de-aggregation in multiwall carbon nanotube (MWNT)/epoxy suspensions [37]. In this work, the slopes of η versus γ at low shear rates are about -0.9, -1.5 and -1.2 for OMMT/SO, GO/SO and Kaolin/SO suspensions, respectively.…”