Functional copolymer/organo-montmorillonite nanoarchitectures. IX. Synthesis and nanostructure-morphology-thermal behaviour relationships of poly[(maleic anhydride)-alt-(acrylic acid)]/organo-montmorillonite nanocomposites

Functional copolymer/clay hybrids were synthesized by radical-initiated interlamellar copolymerization of maleic anhydride/maleic acid and acrylic acid with 2,2'-azobis(2-methylpropionamidine) dihydrochloride as a water-soluble ion-izable radical initiator in the presence of reactive (octadecylamine-montmorillonite (ODA-MMT)) and non-reactive (dimethyldodecylammonium-montmorillonite) organoclays at 60 degrees C in aqueous medium under nitrogen atmosphere. The monomers were dissolved in aqueous medium, and the two types of clay particles used were easily dissolved and dispersed partially swollen, respectively, in deionized water. Structure, thermal behaviour and morphology of the synthesized nanocomposites were investigated using Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and scanning and transmission electron microscopy. It is demonstrated that intercalative copolymerization proceeds via ion exchange between organoclays and carboxylic groups of monomers/polymers, which essentially improves interfacial interactions of polymer matrix and clay layers through strong hydrogen bonding. In the case of intercalative copolymerization in the presence of ODA-MMT clay, a similar improvement is provided by in situ hydrogen bonding and amidolysis of carboxylic/anhydride groups from copolymer chains with primary amine groups of ODA-MMT. The nanocomposites exhibit higher degree of intercalation/exfoliation of copolymer chains, improved thermal properties and fine dispersed morphology. (C) 2011 Society of Chemical Industry