Structure-Property Relationships of Water-Soluble Ammonium-Ionene Copolymers

Water‐soluble random copolymer ammonium ionenes with $\overline{M}_{\rm w}$ in the range of 17.4 to 20.8 kg mol−1 and various charge densities are synthesized from 1,12‐dibromododecane, N,N,N′,N′‐tetramethyl‐1,6‐hexanediamine, and 1,12‐bis(N,N‐dimethylamino)dodecane. Anion exchange of the bromine counterion forms ionenes with TFSI, TFO, and BF4 anions. The nature of the counteranion and charge density tailor the thermal and rheological properties of 12,6/12‐ionenes, respectively. X‐ray scattering reveals microphase separation with a correlation length of ≈7 nm for ionenes with 50 to 90% N,N,N′,N′‐tetramethyl‐1,6‐hexanediamine content. Ionene copolymers display polyelectrolyte behavior in methanol based on a predicted scaling relationship between specific viscosity (ηsp) and concentration. 12,6/12 Random copolymer ammonium ionenes are prepared via the Menshutkin reaction and the effects of charge density on thermal properties, morphology, and solution rheology are studied in detail. The counterion exchange from bromine to larger and weakly coordinated anions require less thermal energy to dissociate the ionic interactions, leading to tailored thermal behavior.