Electrorheological Properties of Polydimethylsiloxane/TiO2-Based Composite Elastomers

Abstract

Electrorheological elastomers based on polydimethylsiloxane filled with hydrated titanium dioxide with a particle size of 100-200 nm were obtained by polymerization of the elastomeric matrix, either in the presence, or in the absence, of an external electric field. The viscoelastic and dielectric properties of the obtained elastomers were compared. Analysis of the storage modulus and loss modulus of the filled elastomers made it possible to reveal the influence of the electric field on the Payne effect in electrorheological elastomers. The elastomer vulcanized in the electric field showed high values of electrorheological sensitivity, 250% for storage modulus and 1100% for loss modulus. It was shown, for the first time, that vulcanization of filled elastomers in the electric field leads to a significant decrease in the degree of crosslinking in the elastomer. This effect should be taken into account in the design of electroactive elastomeric materials.

Keywords: TiO2; crosslinking; nanomaterials; smart materials; stimuli-responsive materials.

Figure 1

The analysis results of titanium dioxide powder obtained by hydrolysis of titanium isopropoxide in ethanol, using (a) XRD (Bragg positions correspond to anatase); (b) SEM; (c) low-temperature nitrogen adsorption. The inset shows the pore size distribution.

Figure 2

Storage modulus ($G^{\prime }$) and loss modulus ($G^{″}$) as functions of relative deformation in electric fields of various strengths (1–0 kV/mm; 2–0.4 kV/mm; 3–1.2 kV/mm; 4–2 kV/mm) for elastomer samples modified with titanium dioxide and vulcanized (a) in the absence of an electric field and (b) in an electric field. The shear rate was 0.1 rad/s.

Figure 3

The effect of the external electric field strength on the value of the Payne effect for the storage modulus ($G_0^{\prime }-G_{\infty }^{\prime }$) and loss modulus ($G_0^{″}-G_{\infty }^{″}$) for the ERE-0 and ERE-5 samples.

Figure 4

The electrorheological sensitivity of composite elastomers (a) ERE-0 and (b) ERE-5 with respect to storage (${\eta }_E^{\prime }$) and loss (${\eta }_E^{″}$) moduli as function of relative deformation at various strengths of an external electric field (1–0.4 kV/mm, 2–1.2 kV/mm, 3–2.0 kV/mm).

Figure 5

The dielectric constants (ε′, ε′′) as functions of frequency for (1) unmodified polydimethylsiloxane and TiO₂-modified polydimethylsiloxane samples: (2) ERE-0; (3) ERE-5.

Figure 6

Cole–Cole diagrams for TiO₂-modified elastomers: (1) ERE-0; (2) ERE-5.

Figure 7

The dielectric constant (ε) and dielectric loss tangent (tgδ) of composite elastomers (1) ERE-0 and (2) ERE-5 as functions of the electric field strength.

Figure 8

Scanning electron microscopy data for composite elastomers (a) ERE-0 and (b) ERE-5 after analysis of the degree of crosslinking of the polymer matrix (after washing in toluene and ethanol).