Gelation And Its Application In Attapulgite/Polymer Nanocomposites Via In-situ Polymerization

In recent years, clay/polymer nanocomposites have attracted more and more attention. The clay/polymer nanocomposites could be prepared by physical blending and in-situ polymerization techniques. Among them, the nano-clays could be dispersed into the polymer matrices as nearly molecular state via the in-situ polymerization technique, thus the better comprehensive performance are obtained.Here, the functional attapulgite nanorods modified by silane coupling agent were used as a multiple cross-linker in the in-situ polymerization to prepare novel attapulgite/polymer nanocomposite with three dimensional network structure. Based on the formation of the three dimensional microgels, novel attapulgite/polymer nanocomposite hydrogels were synthesized, in which the modified attapulgite nanorods act as not only the initiator but also the crosslinker. The obtained attapulgite/polymer nanocomposite hydrogels exhibited high adsorption capacity for organic dyes in wasted water.1. Gelation in the Attapulgite/polystyrene nanocomposites via facile in-situ bulk polymerizationNovel attapulgite/polystyrene nanocomposites (ATP/PS) were synthesized via the facile in-situ bulk radical polymerization of styrene in the presence of the organo-attapulgite nanorods (Org-ATP), which was prepared by modification of the acid-activated attapulgite nanorods (A-ATP) with the functional silane (γ-methacryloxypropyl trimethoxy silane (MPS)). The micro-gels were found in the ATP/PS nanocomposites from the TEM analysis. The effect of the polymerizing condition, such as feeding ratios of the Org-ATP and initiator and N2atmosphere, on the gelation and the thermal properties were investigated. Therefore the optimal preparation condition for the attapulgite/polystyrene nanocomposites (ATP/PS) via the in-situ bulk polymerization was achieved and the crosslinking mechanism to the micro-gels was also depicted. This understanding should lead to better design of clay modifications for use in polymer nanocomposites.2. High clay-content Attapulgite/poly(acrylic acid) nanocomposite hydrogel via surface-initiated redox radical polymerization with modified Attapulgite nanorods as initiator and crosslinker Attapulgite/poly(acrylic acid) nanocomposite (ATP/PAA) hydrogels with high clay content of around90%have been synthesized by a novel surface-initiated redox radical solution polymerization of acrylic acid (AA) with the3-aminopropyltriethoxysilane (KH-550) modified attapulgite nanorods (ATP-NH2) as initiator and the3-methacryloxypropyl-trimethoxysilane (KH-570) modified attapulgite nanorods (ATP-C=C) as cross-linker. High inorganic-content nanocomposite (ATP/PAA) hydrogel with a three-dimensional network structure was obtained via the linkage of the different functional attapulgite nanorods with the grafted poly(acrylic acid)(PAA) chains. Both the two kinds of the functional attapulgite nanorods acted as the cross-linking sites in the nanocomposite hydrogel. Due to its unique structure, a remarkably high adsorption capacity of the cationic dye (methylene blue (MB)) of308.0mg/g was achieved when the ATP/PAA nanocomposite hydrogel was used as the adsorbent for water treatment.3. Preparation of Attapulgite/poly(acrylic acid) nanocomposite hydrogel with bi-functionalized Attapulgite nanorodsThe bi-functionalized Attapulgite nanorods were prepared by modification with two silanes:3-aminopropyltriethoxysilane (KH-550) and3-methacryloxypropyl-trimethoxysilane (KH-570). Then the bi-functionalized Attapulgite nanorods were used as the initiator and crosslinker for the Attapulgite/poly(acrylic acid) nanocomposite (ATP/PAA) hydrogels via a novel surface-initiated redox radical solution polymerization of acrylic acid, in which the-NH2groups were used as the redox initiator with Ce4+, and the-C=C groups were used for the crosslinking. The effects of the different modified attapulgite nanorods, feeding ratios of acrylic acid and Ceric ammonium nitrate on the structure and morphology of the ATP/PAA nanocomposite hydrogels were investigated with FT-IR, TEM, and TGA techniques. Finally, their adsorption property was studied under different pH values.