Conformational Analysis of the Crystal Structure for MDI/ BDO Hard Segments of Polyurethane Elastomers

نویسندگان

  • CHRIS W. PATTERSON
  • DAVID HANSON
  • ANTONIO REDONDO
  • STEPHEN L. SCOTT
  • NEIL HENSON
چکیده

From conformational analysis, we have determined the two lowest energy crystal structures for the hard segments of 4,49-diphenylmethane diisocyanate/1,4butanediol (MDI/BDO)-based polyurethane elastomer. Both crystal forms give prominent X-ray scattering at ;7.6 Å. In one crystal form, (1), there is strong hydrogen bonding between linear chains with a density of 1.30 g/cm, while in the other form, (2), van der Waals bonding gives rise to a double helix structure with a density of 1.22 g/cm and a formation energy 1.6 kJ/mol higher than form (1). The double helix crystal has a unit cell length of 18.8 Å which is about half the 34.7 Å unit cell length of the hydrogen-bonded crystal. The X-ray diffraction predicted for each crystal is presented and compared with experiment. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys

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تاریخ انتشار 1999