An eco-friendly synthesis has been developed for the methylation of tertiary amines to form the quaternary using dimethyl carbonate (DMC)1. The work described here focused on developing the procedure for characterizing rheological behavior, particularly viscosity, of these quaternaries. The effects of temperature, water %, and solvent % on the behavior of the quat were also investigated. Water is known to affect viscosity and these quaternaries are hygroscopic, so samples were prepared in a dry box and transferred to the rheometer in sealed vials. The Brookfield R/S Plus Rheometer was housed in a glove bag to prevent water absorption, and a Karl Fischer Titrator was used to determine the water content of the quat. At 38°C, just above its melting point, the viscosity of tributylmethylammonium methyl carbonate was distinctly non-Newtonian, decreasing with time at constant shear rate or constant shear stress. We speculate that the initial decrease in viscosity was due to the break-up of long range order in the ionic quat.

1Earl, G. W.; Weisshaar, D. E.; Paulson, D.; Hanson, M.; Uilk, J.; Wineinger, D.; Moeckly, S. Quaternary Methyl Carbonates: Novel Agents for Fabric Softening. Journal of Surfactants and Detergents 2005, 8(4), 325-329.