Characterization of systematically selected organo-montmorillonites for polymer nanocomposites

Eight carefully selected organoclays from monoalkyl- to tetraalkylammonium type were prepared from a sodium-saturated < 2 μm fraction of Jelšový Potok bentonite (Slovakia). Four samples contained 1–4 octylammonium chains, from monooctylammonium (1C8) to tetraoctylammonium (4C8). Two cations had chains with 16 carbons each, hexadecylammonium (1C16) and dihexadecyldimethylammonium (2C16). Two cations contained a benzene ring, either without reactive bonds (benzyltrimethylammonium, C10) or with a double bond in 4-vinylbenzyl-trimethylammonium (C12). The d001 values depended on the size and structure of the organocation. The height of the interlayer space in the 1C8–4C8-Mt series increased from 0.45 to 1.68 nm. 2C8 cation opened the interlayer space more than 1C16; 2C16 was more effective than 4C8. Expansion of only 0.55 nm was obtained with C10 and C12. Mass losses between 150 and 800 °C in N2 flow were 13–38% for 1C8–4C8-Mt and 40% for 2C16-Mt. Infrared (IR) spectra were similar for 1C8–4C8-Mt but different for the samples with 16 C and 32 C atoms due to altered ratios of CH3 and CH2 groups. Downward shift of the CH2 stretching bands with increasing size of the alkylammonium cation suggest that alkyl chains adopt more ordered structure. The suitability of the prepared materials to be used as fillers for polymer nanocomposites was assessed according to rheological measurements of dispersions in solvents taking solubility parameters as primary factors for comparison of particular solvent and polymer.