Effect of Clay Surface Charge on the Emerging Properties of Polystyrene–Organoclay Nanocomposites

Abstract

Polystyrene-organoclay nanocomposites, wide angle x-ray scattering, clay, cation exchange 12 capacity (CEC) 13A series of polystyrene-clay nanocomposites, based on two natural clay types (Na-14Montmorillonite and Hectorite), and two synthetic clays (Laponite and Li-Fluorohectorite), were 15 prepared via in situ intercalative polymerization after surface modification with an organic 16 2 ammonium cation (CTAB). The structural characteristics of the organically modified clays as 17 well as the nanocomposites were investigated by means of wide angle x-ray scattering (WAXS), 18 and the thermal properties were studied with TGA. In organically modified clays, the silicate 19 interlayer spacing increases and the magnitude seems to be directly correlated with the amount of 20 clay surface charge. In nanocomposites, polymer intercalation is also observed but partial 21 exfoliation is present, modifying significantly the morphology of the material. The degree of 22 dispersion of the clay platelets, as well as the resulting properties of the nanocomposites, were 23 found again to be systematically, and almost linearly correlated with the intrinsic surface charge 24 of the clays, which varied between 44 and 120 meq/100g. Increased dispersion was seen in the 25 nanocomposites made from clays with low surface charge, here Hectorite and Laponite, 26 suggesting that these can be suitable alternatives to the more employed Montmorillonite for 27 enhancement of thermal properties. The thermal stability was found to be better for the 28 nanocomposites than for the pure polystyrene. 29

Organo-Modified Montmorillonite Enhanced Chemiluminescence via Inactivation of Halide Counterions in a Micellar Solution

“…The first weight loss at 100 °C was obtained from the water molecules at the surface of the MMT particles and in the MMT interlayers, following by the decomposition of the CTA + monolayer at the MMT surface from 200 to 300 °C, and in the MMT interlayer from 300 to 400 °C. The last weight loss between 400 and 500 °C was corresponded to the loss of the polyhydroxyaluminum. , In comparison to the original CTAB-modified MMT, the DTG curve of the washed CTAB-modified MMT showed no weight loss between 200 and 300 °C, indicating the disappearance of the CTA + monolayer. These findings were in accordance with those obtained by ζ potential measurements (please see Figure S7, Supporting Information).…”

“…The last weight loss between 400 and 500 °C was corresponded to the loss of the polyhydroxyaluminum. 35,36 In comparison to the original CTAB-modified MMT, the DTG curve of the washed CTAB-modified MMT showed no weight loss between 200 and 300 °C, indicating the disappearance of the CTA + monolayer. These findings were in accordance with those obtained by ζ potential measurements (please see Figure S7, Supporting Information).…”

Clay nanolayer encapsulation, evolving from origins of life to future technologies

“…There are several cases investigated and reported in the literature with respect to capturing and retention mechanisms for encapsulation of foreign molecules inside such clay interlayers ( Fig. 6), including H 2 O intercalation [12,13,[39][40][41][42][43][44][45][46], CO 2 capture and retention [36,[47][48][49][50][51], cation exchange [12,13,52], medical drug capture and release [12,13,39,[53][54][55][56][57][58][59], capture of surfactants [12,13,39,60,61], polymers [12,13,39,[62][63][64], or nanoparticles [65]. These encapsulation properties of clay nanolayered stacks are crucial for several engineering applications, e.g.…”

Increasing time of ignition for PS-clay nanocomposites filled with [Fe(bpy)3]2+-modified hectorite

“…The problem can be eased by applying phosphonium that typically show an onset of degradation at 250 C but these compounds are rather expensive. When looking at flame retardancy, the thermal lability of the modifier transforms in a significantly reduced time of ignition (t ig ) [12], even more so for clay of high charge density for which more modifier becomes attached [7,13]. For instance, for PS-clay nanocomposites of a synthetic Lihectorite with very high cation exchange capacity a pronounced reduction of t ig from 42 s for polystyrene to 26 s for the nanocomposite was reported [7].…”