Significant decreased dielectric constant and loss of polystyrene–clay nanocomposite materials by using long‐chain intercalation agent

Abstract

Polystyrene-clay nanocomposite (PsCN) materials have been prepared by a free radical polymerization process. Montmorillonite (MMT), modified by two different organics, was investigated: one contains a short chain and three benzyl groups on the ammonium ion (DAETPB), while the other contains a long chain (HTAC). The organic modification determines the extent of exfoliation or intercalation of the materials. Exfoliation is more likely to occur using HTAC, as then the gallery of clay has been opened more due to the long chain structure. Exfoliation of MMT in polystyrene (PS) matrix was revealed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were employed to confirm the increased thermal stability of these PsCN materials. Dielectric properties of polystyrene-clay nanocomposites, in the form of film with clay loading from 1.0 to 5.0 wt %, were measured under frequencies of 100 Hzϳ1 MHz at 25ϳ70°C. Decreased dielectric constant and low dielectric loss were observed for PsCN materials. Especially, the decrease of dielectric constant was found to be related to the extent of exfoliation of clay. It is recognized that the confinement effect of clay results in the suppression of the dielectric response of the nanocomposite materials at low frequency.

Investigation of correlation between dielectric parameters and nanostructures in aqueous solution grown poly(vinyl alcohol)-montmorillonite clay nanocomposites by dielectric relaxation spectroscopy

“…The present dielectric study also confirms that a large reduction of the ε s and also the increase of τ value at 1 wt% MMT clay loading results in the formation of large range crosslinked hydrogen bonded structures between exfoliated MMT clay sheets and the randomly coiled and flexible PVA chains, which reduces the net dielectric polarization and increases the hindrance to the PVA local chain dynamics. Wang et al [20] also concluded that a large amount of exfoliated MMT clay structures in PCNs enhances the T g value and simultaneously reduces the ε s value. The increase in τ value is also related to the increased amount of layered silicate surface area as a result of the increased degree of exfoliation [24,28].…”

“…Further, the formation of the hydrogen bonds between the PVA vinyl alcohol group and silicate oxygen force the PVA chains to create long adsorbed trains due to the atomically smooth dispersed MMT surfaces. The large reduction in ε′ value at 1 wt% MMT clay concentration in PVA-MMT clay nanocomposites also suggests that the amount of exfoliated structures is very high as compared to that of the PVA intercalated clay structures [14,15], which is the common characteristics of solution grown PCNs at very low clay concentration [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. The loss part ε″ spectra of complex dielectric function ( Figure 1b) reflects the presence of two relaxation processes in the PVA-MMT clay nanocomposite films over the frequency range 20 Hz-1 MHz, which can be seen in their complex plane plots (ε″ vs. ε′) (Figure 2).…”

“…This behaviour is not surprising, because in aqueous solutions the flexible PVA chain and dispersed clay exist with a variety of hydrogen bonded structures. Recently, Wang et al [20,21] investigated the dielectric properties of solution intercalated polystyrene-MMT clay and poly(methyl methacrylate)-MMT clay nanocomposite films within the frequencies of 100 Hz-1 MHz and found that loading of 1 wt% MMT clay significantly reduces the ε′ values as compared to the pure polymer film, which is mainly due to reduction in the number of aligned dipolar groups in the presence of randomly distributed exfoliated clay nanoplatelets in the polymer matrix. In PVA-MMT clay nanocomposites, the intercalation of PVA in clay galleries and exfoliation of MMT clay nanoplatelets occur simultaneously [13][14][15][16][17].…”

“…The complex dielectric function, alternating current (ac) electrical conductivity, impedance properties and electric modulus spectra of the PVA-MMT clay nanocomposite films were investigated over the frequency range 20 Hz to 1 MHz. An attempt is made to correlate the values of various dielectric parameters with structural behaviour of these nanocomposites materials to establish the use of dielectric relaxation spectroscopy as diagnostic tool for the development of on-line testing and monitoring of the nanocomposite formation in PCNs materials [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

Novel Silica Tube/Polyimide Composite Films with Variable Low Dielectric Constant

“…In previous studies, the dielectric constant in clay/polystyrene decreases monotonically from 12 to 5 at 1 MHz with increasing clay content up to 2.5 wt.-%, [19] and the dielectric constant of the layered silicate/PI nanocomposites demonstrates a monotonic increase from 2.68 to 3.07 at 1 MHz as the silicate content increases from 0 to 5.0 wt.-%. [16] The dielectric constants of both the silica particle/PI composites and the CNT/polymer composites increase with the increase of inclusion content.…”