Polyurethanes containing sulfur. III. New thermoplastic HDI‐based segmented polyurethanes with diphenylmethane unit in their structure

Abstract

AbstractThree series of new thermoplastic, high molecular weight, segmented thiopolyurethanes were synthesized by a one‐step melt polymerization from newly obtained thiodiols, including bis[4‐(2‐hydroxyethyl)thiomethylphenyl]methane, bis[4‐(3‐hydroxypropyl)thiomethylphenyl]methane, and bis[4‐(6‐hydroxyhexyl)thiomethylphenyl]methane (BHHM), as chain extenders; hexamethylene diisocyanate; and 20–80 mol % poly(oxytetramethylene) glycol (PTMG; number‐average molecular weight = 1000) as the soft segment. Solution polymerization with the chain extender BHHM gave considerably lower molecular weight polymers. The structures of all the polyurethanes were determined with Fourier transform infrared and X‐ray diffraction analysis. The thermal properties of the polyurethanes were examined with differential scanning calorimetry and thermogravimetric analysis. Shore A/D hardness and tensile properties were also determined. All the polyurethanes showed partially crystalline structures; those obtained with 40–80 mol % PTMG were elastomers. An increase in the PTMG content decreased hardness, modulus of elasticity, and tensile strength, whereas elongation at break increased. BHHM‐based polyurethanes obtained in the melt showed the best tensile properties. The polyurethanes exhibited definite glass transitions (−70 to −59 °C) that were nearly independent of the hard‐segment content up to about 50 wt % (40–80 mol % PTMG), indicating the existence of mainly microphase‐separated soft and hard segments. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1733–1742, 2001