Model MDI/butanediol polyurethanes: Molecular structure, morphology, physical and mechanical properties

Abstract

Abstract Model butanediol–MDI–polypropylene oxide polymers have been synthesized to explore the structure–property relationships in urethane/polyether polymers. The results of mechanical, thermal, and spectroscopic analyses agree remarkably well. The phase mixing in these polymers decreases with increasing hard‐segment length, while the hard‐segment stability increases with increasing hard‐segment length. This is demonstrated clearly by dynamic mechanical, differential scanning calorimetry, infrared, and NMR studies. The importance of hydrogen bonding to the stability of the hard segment is strongly supported by the variable‐temperature infrared experiments. The critical hard‐segment size for phase segregation was shown to be two butanediols per hard segment. The temperature limit of the flatness of the storage modulus was tied to the thermal stability of the hard‐segment hydrogen bonding which is controlled largely by the length of the hard segment and the extent of the hydrogen bonding.