Morphology and properties of polybutadiene‐ and polyether‐polyurethane zwitterionomers

Two series of polyurethane zwitterionomers based on 4,4′‐methylene‐di(phenyl isocyanate) (MDI), N ‐methyl diethanolamine (MDEA) Systematic IUPAC name: 2,2′‐(methylimino)diethanol. , and either 1350 molecular weight hydroxyl terminated polybutadiene or 1000 molecular weight poly(tetramethylene oxide) Systematic IUPAC name: poly(oxytetramethylene). were synthesized. Zwitterionization was accomplished by quaternizing the tertiary amine of MDEA with 1,3‐pro‐panesultone. In Both series, IR analysis suggests that the sulfonate ion SO 3 − associates with the counter ion on the chain extender and the acidic hydrogen of the urethane linkage. Ammonium sulfonation shifts the soft segment T g of polyether‐based material to lower temperatures suggesting that ionization improves microphase separation. The soft segment T g of the polybutadiene system is unaffected by ionization. IR dichroism measurements show that with increasing ammonium sulfonation both the hard and soft segments in the polyether‐polyurethane zwitterionomers orient to a greater extent with deformation. In contrast, in the poly‐butadiene‐based zwitterionomers the orientability of the hard segment decreased with ionization while the soft segment showed significant chain alignment. Coupling the dichroism measurements to stress‐strain results suggests that the hard segment domains of the polyether‐polyurethane system possess more of an interconnected structure, while the polybutadiene‐poly‐urethane system contains hard segment domains which are largely isolated. The formation of different morphologies in the two systems of zwitterionomers may be due to the different interdomain surface tensions.