Synthesis and Characterization of Low-Generation Polyamidoamine (PAMAM) Dendrimer–Sodium Montmorillonite (Na-MMT) Clay Nanocomposites

Abstract

Polymer-inorganic nanocomposites are a recently developed class of materials that have altered physical or chemical properties with respect to the pure polymer, inorganic host, or their micro- and macrocomposites. Lower generation (G0.0-2.0) polyamidoamine (PAMAM) dendrimer/sodium montmorillonite (Na-MMT) nanocomposites were synthesized in a solution-phase exfoliation adsorption reaction. These are the first reports of the G0.0/ and G1.0/Na-MMT nanocomposites and of a structurally-ordered G2.0/Na-MMT. The materials were characterized using powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). PAMAM characteristics at acidic and basic aqueous media were studied using capillary zone electrophoresis (CZE). Pseudospherical PAMAM dendrimers in aqueous medium attain a highly flattened conformation within the confined space between MMT sheets upon nanocomposite formation. The nanocomposite structure depends on the PAMAM generation and the starting dendrimer/organic composition. G0.0 always forms monolayer structures (d = 0.42 nm), while G2.0 forms monolayer structure, mixed phase, and bilayer structures (d = 0.84 nm) at lower, intermediate, and higher organic content, respectively, showing an interesting monolayer to bilayer transition. G1.0 showed an intermediate behavior, with monolayer to mixed-phase transition at the reactant ratios studied. This monolayer arrangement of PAMAM/clay nanocomposites is reported for the first time. Maximum organic contents of G0.0 monolayer and G2.0 bilayer nanocomposites were ∼7% and ∼14%, respectively. Gallery expansions were similar to those observed with linear polymer intercalates, but the packing fractions (0.31-0.32) were 2-3 times lower. At acidic pH, the nanocomposites forming only monolayer structures are obtained, indicating a stronger electrostatic attraction between MMT and protonated PAMAM, and these nanocomposites formed more slowly and were more ordered. Na(+) ions play a significant role in nanocomposite formation. At high pH, PAMAMs show high mobility, ζ potential, and surface charge densities due to Na(+) complexation in solution. FTIR data indicates that both Na-MMT and PAMAM structural units are preserved in the nanocomposites obtained.

Synergistic stabilization of shale by a mixture of polyamidoamine dendrimers modified bentonite with various generations in water-based drilling fluid

“…1(c) and (d)). This phenomenon was also observed by Liyanage et al (2013). Aggregation of the dendrimer molecules in the interlayer space resulted in the formation of mixed phase.…”

“…The temperature ranging from 200°C to 350°C was associated to the degradation of the PAMAM (Azzouz et al, 2013; Liyanage et al, 2013). The mass loss for the PAMAM dendrimer modified bentonite composites in this step was 2.2%, 2.0%, 2.7%, 2.5%, 2.0% and 2.3% respectively with the dendrimer concentration of 0.1%(w/v), and 8.0%, 9.4%, 12.1%, 14.5%, 12.9%, and 13.8% with the dendrimer concentration of 2%(w/v).…”

Fluorescence microscopy as an alternative to electron microscopy for microscale dispersion evaluation of organic–inorganic composites

“…3b ). In comparison with the Na + -MMT, the TPE-DTAB-modified MMT exhibited two new absorption bands at 2,926 and 2,855 cm −1 , which were ascribed to the asymmetrical and symmetrical stretching vibrations of methylene groups in the alkyl chains of TPE-DTAB, respectively 50 . Moreover, the absorption intensity at 3,624 cm −1 of the TPE-DTAB-modified MMT was lower than that of the Na + -MMT because of the improved hydrophobicity 51 .…”

Probing the confining effect of clay particles on an amorphous intercalated dendritic polyester

“…Recently, layer-by-layer intercalation of flattened Boltorn TM HBPs into Na + MMT clay galleries was confirmed by Androulaki et al [29]. Analogous behavior was observed for Na + MMT clay based nanocomposites with a hyperbranched polyesteramide (Hybrane TM ) and a polyamidoamine (PAMAM) dendrimer, each prepared via aqueous solution intercalation methodology [30][31].…”