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Conformational analysis of the crystal structure for MDI/BDO hard segments of polyurethane elastomers

✍ Scribed by Chris W. Patterson; David Hanson; Antonio Redondo; Stephen L. Scott; Neil Henson

Publisher: John Wiley and Sons
Year: 1999
Tongue: English
Weight: 354 KB
Volume: 37
Category: Article
ISSN: 0887-6266
DOI: 10.1002/(sici)1099-0488(19990901)37:17<2303::aid-polb2>3.0.co;2-o

No coin nor oath required. For personal study only.

✦ Synopsis

From conformational analysis, we have determined the two lowest energy crystal structures for the hard segments of 4,4Ј-diphenylmethane diisocyanate/1,4butanediol (MDI/BDO)-based polyurethane elastomer. Both crystal forms give prominent X-ray scattering at ϳ7.6 Å. In one crystal form, (1), there is strong hydrogen bonding between linear chains with a density of 1.30 g/cm 3 , 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 3 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.

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