Polymer Nanocomposite of Mg-Al Hydrotalcite-Type Anionic Clay Modified with Organosulfate

Abstract

The Mg-Al hydrotalcite (HT) was modified with organosulfate, sodium dodecylsulfate (SDS) by an anion exchange reaction. The modifier content and the interlayer distance of organo-modified HT (MHT) were examined. The modifier content and dspacing in HT layers increased up to 45% of AEC and 38.0 Å . Incorporation of the modifier in HT layers at pH 7 was easier than at pH 11, due to the higher concentration of anions in HT layers at pH 11 than at pH 7. Polystyrene(PS) and poly(methyl methacrylate)(PMMA) nanocomposites with the MHT were prepared by solution and melt blending, and in situ polymerization; an intercalation and partially exfoliation were obtained together with thin packets of HT layers. The partially exfoliated PMMA/MHT nanocomposites were obtained even at the 5 wt % MHT loading. The nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The mechanical properties of nanocomposites were also investigated.KEY WORDS: Mg-Al hydrotalcite / Organosulfate / Nanocomposite / PMMA / PS / Polymer/layered inorganic nanocomposites (PLN) have attracted great interest in the field of material chemistry because of their novel mechanical, thermal, and optical properties, 1-8 which are mainly attributed to the high degree of dispersion of layered inorganic compounds in the polymer matrix. A mass fraction of a few percent of reinforcing agent that is properly distributed in the polymer matrix creates significantly more surface area for polymer-filler interactions than do conventional composites.9 Among PLNs, exfoliated PLN materials usually have a molecular dispersion of high aspect ratio inorganic layers in polymer nanocomposites. 10Silicate clays such as montmorillonite, hectorite, and magadiite are the most common fillers used for the preparation of nanocomposites; they have a layered structure with 1 nm thickness and extremely high aspect ratios (e.g. 50-1000). 11Lately, a new emerging class of nanocomposites, based on anionic hydrotalcite (HT)-like clays, has been investigated.Anionic clays can be considered the opposite of silicate clays; positively charged sheets are stacked one on top of the other and intercalated by exchangeable anions and water molecules.12 HTs are positively charged due to the isomorphous substitution of bivalent cations by trivalent ones. The layers are intercalated with anions in order to balance the residual charge. One of the most important properties of the HT-type material is its high anionic exchange capacity related to its lamellar structure that allows the exchange of its original anions with those present in an aqueous solution.It is well known that HT-type compound belongs to the large class of natural and synthetic HT. HT have the generalxþ A x/z zÀ . mH 2 O, where M is a metal cation and A is an exchangeable anion. Typically LDH anion exchange capacities vary in the range of 200-470 mequiv/100 g and are higher than the corresponding cation exchange capacity of silicate clays like sodium montmorillo...

Structural Characterisation of Complex Layered Double Hydroxides and TGA‐GC‐MS Study on Thermal Response and Carbonate Contamination in Nitrate‐ and Organic‐Exchanged Hydrotalcites

“…Hydrotalcites (anionic clays) are inorganic natural or synthetic layered double hydroxides (LDHs) containing exchangeable anions. The increasing interest in these materials is due to their numerous applications, such as catalysis, [1] preparation of pigments, [2] removal of wastes ubstances from water, [3][4][5][6][7] polymer additives, [8][9][10][11] pharmaceutical, nutraceutical and cosmetic formulations, [12,13] symptomatic treatment of peptic ulcers [10,11] and therapy of digestive disorders, [12] hosts for drugsa nd biomolecules [17][18][19] and CO 2 sequestration. [20,21] Especially the numerous applications in the field of human health have raised much interesti nt hese inorganic materials, but at the same time careful and extensive studies are necessary to understand the reactivity,m echanismo fa ction and toxicity.…”

Compósitos de Poliestireno e Argila Aniônica Funcionalizada com Cinamato com Propriedade de Absorção de UV

“…O processo de obtenção de nanocompósitos envolve o estabelecimento da compatibilidade entre a carga inorgânica, de natureza hidrofílica e a matriz polimérica. No caso de utilizar um polímero hidrofóbico, como o poliestireno (PS), a modificação química da superfície dos LDH pela ação de agentes químicos contendo grupamentos orgânicos aniônicos pode reduzir as forças repulsivas e aumentar a compatibilidade da argila com o polímero, promovendo a dispersão e a intercalação das cadeias poliméricas, podendo até mesmo resultar em delaminação [8][9][10][11] . Alguns ânions orgânicos tais como, carboxilatos, sulfatos e sulfonatos, podem ser facilmente intercalados [11,12] .…”

Transparent Poly(methyl methacrylate)/TiO₂ Nanocomposites for UV-Shielding Applications

“…Incorporation of a small amount of inorganic nanoparticles can dramatically improve the bulk performance of polymer matrix in mechanic, thermal, optical, electrical properties etc. [12][13][14][15] Therefore, such nanocomposites have been considered as excellent candidates for UV-shielding applications. Zinc oxide (ZnO) and titanium dioxide (TiO 2 ) are two wide band gap semiconductors that have been widely used as inorganic UV absorbers due to their remarkable optical properties and environmentally friendly nature.…”