Specific Interactions in Polyurethane Cationomers

Studies have shown that addition of cationic groups to a segmented polyurethane can dramatically change physical attributes such as solution behavior, mechanical strength, and viscoelastic properties. However, the specific interactions responsible for these changes are not well understood. A series of polyether polyurethane cationomers were synthesized using chain extenders with pendant trialkylammonium groups. The morphology and properties of the cationomers were studied as a function of ion-related variables using small-angle X-ray scattering (SAXS), tensile testing, dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC). Ion content affected phase separation and mechanical properties the most; the alkyl group length was of secondary importance; and the type of neutralizing anion had essentially no effect. Further, a lamellar microstructure typical of conventional polyurethanes was evident, with no apparent aggregation of ionic groups.