New nanocomposite materials from kaolinite as a mineral precursor.

Abstract

New thermally resistant nanocomposite organokaolinite material have been prepared and characterized. The preparation method for these materials generally involves first expanding the kaolinite interlayers with an intercalating agent such as dimethyl sulfoxide, followed by reaction with a given reagent in the interlayer space of the expanded kaolinite. In many cases the interlamellar surface of kaolinite was chemically modified through the grafting of organic units on the mineral surface. One new class of organokaolinite material was proposed to be formed through the interlayer condensation reaction between an alcohol group of the attacking species and an interlayer surface aluminol group of the kaolinite host to form Al-O-C linkages between the mineral and the organic components. In this manner, new chemically robust methoxy and ethylene glycol functionalized organokaolinites were prepared, with basal spacing of 8.2 A and 9.4A respectively. Furthermore, a new family of oxyethylene (-OCH$\sb2$CH$\sb2$-) based organokaolinite material was prepared and characterized. These materials include the species 15-crown-5 and 18-crown-6 as well as polyethylene glycol chains (MW 3400) which have been successfully incorporated into the interlayers of kaolinite. The products exhibit well defined basal spacings ranging from 10.8 Ato 11.2 A, indicative of a 3.6-4.0 A, layer expansion due to a flattened monolayer arrangement of the oxyethylene units. The materials were generally stable up to temperatures greater than 250$\sp\circ$C in both nitrogen and air atmospheres, but the oxyethylene component could be leached out in refluxing water. Finally, some promising exploratory work involving the functionalization of the interlamellar surface of kaolinite with aminoalcohols, carboxylic acid derivatives and other reagents is presented.