Effects of cyclic and acyclic amidine side-chains on the properties of polysiloxane ionomers constructed in situ from three uncharged components

Abstract

Ionomers, polysiloxanes with imidazolinium dithiocarbamate side chains, have been synthesized in situ from three uncharged components—a polysiloxane with imidazole side chains, CS₂, and hexylamine or octadecylamine. Their structural and dynamic properties are compared over a temperature range of 0–50 °C with those of the analogous ionomers in which the polysiloxanes have amidinium side chains. The results, primarily from differential scanning calorimetry, powder X-ray diffraction measurements, and rheology show that the small structural (and smaller electronic) differences between the cyclic 5-membered ring imidazolinium and acyclic amidinium groups have marked effects on the bulk properties of the ionomers. These include their shear strengths and the manner in which the microcrystalline portions of the ionomers with dithiooctadecylcarbamate anions are packed. Thus, it is possible to finely tune the natures of the ionomers from one polysiloxane by changing temperature, the chain length of the alkylamine, and the nature of the base attached to the polysiloxane chain. Why these changes occur to the various properties is discussed.