Morphology and Structure of Amino Fatty Acid Intercalated Montmorillonite

Abstract

For nanocomposite production, montmorillonite clays are often modified with organic surfactants to favor its intermixing with the polymer matrix. In the present study, Na+-montmorillonite (Na+-MMT) was subjected to organo-modification by cation exchange with protonated 12-aminolauric (ALA). The amount of the amino fatty acid surfactants loaded were 25, 50, 100 and 200% times the CEC of Na+-montmorillonite. X-ray diffraction (XRD) analysis revealed the interlayer spacing of the clay increased from 1.25 to 1.82 nm with increasing ALA content. The amino fatty acid chain were considered to be arranged into a flat monolayer structure at low surfactant loading, while they form a bilayered to a pseudotrilayered structure at high surfactant loading. Infrared spectroscopy (FTIR) revealed the alkylchains adopt a gauche conformation indicating their disordered state. Thermogravimetric analyses (TGA) revealed that the surfactant in the clay were thermally stable with Td ranging from 353 to 417°. The difference in the melting behavior of the pristine fatty amino fatty acids and confined fatty acids in the interlayer galleries of the clay were evaluated differential scanning calorimerty (DSC). The melting temperatures (Tm) of the amino fatty acid in the clay were intitially higher than the free amino fatty acid but decreased with increasing surfactant loading. The amino fatty acid may be tethered to the clay structure via ionic interaction or ion-dipole attraction. Scanning electron microscopy (SEM) revealed that the organo-clays have a disordered and flaky morphology. The present study suggests that 12ALA is a suitable intercalating agent for the production of organophilic clay materials.