The interest in charge-containing polymers, commonly referred to as ionenes , has increased significantly over the past decade due to their potential application in areas such as electroactive devices and membrane separation sciences.   Here, we report the synthesis and thermal properties (Tg and Td) of several imidazolium-containing thermoplastic polyurethanes. During the course of this study, three key structural deviations were explored:  (1) counteranion selection (size and/or hydrogen bonding capability) (2) NCO:OH ratio (hard segment content) and (3) charge density (mono- vs. bis-substitution).  The polyurethanes were prepared by reacting an isocyanate prepolymer (polymeric MDI and poly(propylene glycol) oligomer) with an imidazolium-containing diol chain extender.  In general, we observed that counteranion selection had a tremendous effect on thermal properties, with larger anions leading to depressed Tg values while use of anions with weak hydrogen bonding affinity resulted in the highest thermal stability (Td). Increasing the hard segment (NCO content) generally led to an increase in Tg and Td values while increasing the number of imidazolium rings from one to two per monomeric unit led to depressed Tg values and little change in thermal stability.

Imidazolium-containing polyurethanes: Deciphering the relationship between structure and thermal properties

246th National Meeting (2013)

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