Electric Field-Responsive Mesoporous Suspensions: A Review

Abstract

This paper briefly reviews the fabrication and electrorheological (ER) characteristics of mesoporous materials and their nanocomposites with conducting polymers under an applied electric field when dispersed in an insulating liquid. Smart fluids of electrically-polarizable particles exhibit a reversible and tunable phase transition from a liquid-like to solid-like state in response to an external electric field of various strengths, and have potential applications in a variety of active control systems. The ER properties of these mesoporous suspensions are explained further according to their dielectric spectra in terms of the flow curve, dynamic moduli, and yield stress.

Keywords: electrorheology; mesoporous; nanocomposite; suspension.

Figure 1

Schematic diagram of the electrorheological (ER) phenomenon under an applied electric field.

Figure 2

(a) Proposed schematic diagram of conducting polymer/Mobil Composition of Matter No. 41 (MCM-41) nanocomposite particles (Reproduced with permission from [58]. Copyright Elsevier, 2009); (b) in which the conducting polymer can be polyaniline (Reproduced with permission from [56]. Copyright American Chemical Society, 2004).

Figure 3

(a) Scanning electron microscopy (SEM) and (b) transmission electron microscopy (TEM) image of MCM-41 particles (Reproduced with permission from [47]. Copyright Elsevier, 2000); (c) SEM images of copolyaniline (COPANI)/MCM-41 particles (Reproduced with permission from [58]. Copyright Elsevier, 2009); (d) PPy/MCM-41 particles (Reproduced with permission from [60]. Copyright Elsevier, 2008).

Figure 4

(a) X-Ray diffraction (XRD) patterns of pure and swollen MCM-41 (Reproduced with permission from [57]. Copyright Elsevier, 2005); (b) polymer modification MCM-41 particles (Reproduced with permission from [55]. Copyright Elsevier, 2008).

Figure 5

N₂ adsorption-desorption isotherm plots before polymerization, MCM-41 (●) and swollen MCM-41 (▼); after polymerization, COPANI/swollen MCM-41 (▲) and PANI/MCM-41 (■), respectively (Reproduced with permission from [58]. Copyright Elsevier, 2009).

Figure 6

(a) Shear stress curve as a function of the shear rate for PPy/MCM-41 ER fluids (triangle) and MCM-41-based ER fluid (circle) under different applied electric fields. (Reproduced with permission from [78]. Copyright Elsevier, 2006); (b) Fitting curve of the model equations to shear stress curves for PPy/MCM-41 nanocomposite-based ER fluids under three different electric field strengths (Reproduced with permission from [59]. Copyright Elsevier, 2010).

Figure 7

(a) Dynamic yield stress of MCM-41-based ER fluids at four different electric field strengths; (b) Dynamic yield stress of PPy/MCM-41-based ER fluids at seven different electric field strengths (Reproduced with permission from [59]. Copyright Elsevier, 2010); (c) $\widehat{\mathsf{\tau }}$ vs. $\widehat{E}$ for pure MCM-41 and PPy/MCM-41-based ER fluids. The solid line is drawn with Equation (5).

Figure 8

(a) Strain amplitude sweep of PANI/MCM-41 particles; (b) Angular frequency sweep of PANI/MCM-41 particle under 1 (■) and 2 (●) kV/mm using a strain of 3 × 10⁻⁵: Storage modulus (closed) and loss modulus (open) (Reproduced with permission from [56]. Copyright American Chemical Society, 2004).

Figure 9

(a) Dielectric spectra (permittivity versus frequency); (b) Cole-Cole plot for each ER fluid (Reproduced with permission from [56]. Copyright American Chemical Society, 2004).