Synthesis and characterization of ion-containing poly(urethane-urea-imide) block copolymers

Poly(etherurethane-urea-imide) (PEUUI) block copolymers containing a tertiary amine have been synthesized by reaction of amine-terminated poly(etherurethane-urea) (PEUU) prepolymer with 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA) followed by solution imidization. The amine-terminated PEW prepolymer was prepared using poly(tetramethylene oxide) of molecular weight 2000 as soft segment, toluene diisocyanate (TDI), N-methyldiethanolamine (MDEA), and 4,4-oxydianiline (ODA). The PEUUI block copolymer was converted to ionomer by quaternizing the tertiary amine of MDEA with different diacids and alkyl halides. Properties of PEUUI ionomer films cast from solution were studied by infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis and stress-strain testing. The quaternization of PEUUI shifted the soft segment glass transition temperature (T-g) of PTMO to a lower temperature with subsequent development of hard segment ordering in comparison to nonquatemized PEUUI. The morphological changes of PEUUI upon quaternization were accompanied by dramatic improvements in mechanical properties and dynamic modulus that was extended to much higher temperatures. The mechanical properties and thermal transitions were found to depend on the nature of quaternizer, provided that the system exhibited a two-phase interconnecting morphology. The improved mechanical properties and lowered soft segment T-g of PEUUI ionomer samples were due to increased hard domain cohesiveness caused by ionic interchain interactions and aggregation of ionic groups.