Three series of segmented polyurethanes were synthesized，which are based on 4

4’-methylene-di(phenyl isocyanate) (MDI)，N-methyl diethanolamine (MDEA) and hydroxy terminated poly-butadiene，poly (propylene oxide) or poly (ethylene oxide)．The tertiary amine of MDEA was sulfonated with γ-propane sultone，thereby converting these polyurethanes into zwitterionomers. The effects of the chemical composition and the level of ammonium sulfonation on the extent of phase separation，physical properties and morphologies were studied using differential scanning calorimetry，dynamic mechanical analysis，stress-strain testing and IR spectrometry．The results show that：1，For the polyurethanes studied，the miscibility of different soft segments with hard seg-ment is in the order of PEO>PPO>PBD．The PEO polyurethane is nearly homogeneous but the material based on PBD exhibits almost complete microphase separation．2．Ammonium sulfonation shifts the soft segment Tg of PPO and PEO based polymers to lower temperatures，suggesting that ionization improves microphase separation．The soft segment Tg of the polybutadiene system is uneffected by ionization．The tensile properties are improved dramatically with increasing the degree of ionization．3，IR analysis showed that the sulfonate ion SO2 not only associated with the counter ion一N—on the chain extender but also formed hydrogen bond with—NH of urethane linkage．