Polyurethanes containing sulfur. I. New thermoplastic polyurethanes with benzophenone unit in their structure

New thermoplastic nonsegmented thiopolyurethanes were obtained from the low -melting aliphatic-aromatic thiodiols 4,4'-bis(2-hydroxyethylthiomethyl)ben zophenone (BHEB), 4,4'-bis(3-hydroxypropylthiomethyl)benzophenone (BHPB), a nd 4,4'-bis(6-hydroxyhexylthiomethyl)benzenophenone(BHHB) as well as hexame thylene diisocyanate (HDI), both by melt and solution polymerization with d ibutyltin dilaurate as the catalyst. The effect of various solvents on mole cular-weight values was examined. The polymers with the highest reduced vis cosities (0.63-0.88 dL/g) were obtained when the polymerization was carried out in a solution of tetrachloroethane, N,N-dimethylacetamide, and N,N-dim ethylacetamide or N,N-dimethylformamide for BHEB-, BHPB-, and BHHB-derived polyurethanes, respectively. These polymers with a partially crystalline st ructure showed glass-transition temperatures (T-g) in the range of -1 to 39 degrees C, melting temperatures (T-m) in the range of 107 to 124 degrees C , and thermal stabilities up to 230 to 240 degrees C. The BHEB-derived poly urethane is a low-elasticity material with high tensile strength (ca. 50 MP a), whereas the BHPB- and BHHB-derived polyurethanes are more elastic, show ing yield stress at approximately 16 MPa. We also obtained segmented polyur ethanes by using BHHB, HDI, and 20 to 80 mol % poly(oxytetramethylene) glyc ol (PTMG) of (M) over bar(n) = 1000 as the soft segment. These are high-mol ecular thermoplastic elastomers that show a partially crystalline structure . Thermal properties were investigated by thermogravimetric analysis and di fferential scanning calorimetry. The increase in PTMG content decreases the definite T-g and increases the solubility of the polymers. These segmented polyurethanes exhibit the definite T-g (-67 to -62 degrees C) nearly indep endent of the hard-segment content up to approximately 50 wt %, indicating the existence of mainly phase-separated son and hard segments. Shore A/D ha rdness and tensile properties were also determined. As the PTMG content inc reases, the hardness, modulus of elasticity, and tensile strength decrease, whereas elongation at break increases. (C) 1999 John Wiley & Sons, Inc.