TY - JOUR
T1 - Isotactic polypropylene, β-phase
T2 - A study in frustration
AU - Dorset, D. L.
AU - McCourt, M. P.
AU - Kopp, S.
AU - Schumacher, M.
AU - Okihara, T.
AU - Lotz, B.
N1 - Funding Information:
Research was supported in part by a grant (to DLD) from the National Science Foundation (CHE94-17835) which is gratefully acknowledged. M. Schumacher was supported by a grant from Exxon Chemical International and T. Okihara acknowledges support from the CNRS and the Japanese Ministry of Education. One of us (DLD) also acknowledges fruitful discussions of this problem with Dr S. V. Meille, including his presentation of energy calculations for various choices of space group (NATO ASI on Electron Crystallography held at Erice, Sicily, 22 May to 2 June 1997), favouring P3 1 as one of the most probable space groups. Also, thanks are due to Dr G. D. Smith for discussing his recent work on the twinning of a trigonal form of insulin as well as for pointing out related literature in the protein field.
PY - 1998/12
Y1 - 1998/12
N2 - The three-dimensional crystal structure of isotactic polypropylene in its β-polymorphic form has been refined against electron diffraction intensity data. Microtwinning by merohedry, probably in two antichiral domains in space groups P31 and P32, was identified by sharp continuous diffraction in h0l patterns from epitaxially crystallized samples. Nevertheless, a rather simple model of a frustrated chain packing could be improved by Fourier methods even though the solution of the structure by direct methods was itself frustrated by the extensive overlap of Fhk0 and Fkh0 or Fhkℓ and Fhk,-ℓ amplitudes which led initially to a false prediction of space group symmetry.
AB - The three-dimensional crystal structure of isotactic polypropylene in its β-polymorphic form has been refined against electron diffraction intensity data. Microtwinning by merohedry, probably in two antichiral domains in space groups P31 and P32, was identified by sharp continuous diffraction in h0l patterns from epitaxially crystallized samples. Nevertheless, a rather simple model of a frustrated chain packing could be improved by Fourier methods even though the solution of the structure by direct methods was itself frustrated by the extensive overlap of Fhk0 and Fkh0 or Fhkℓ and Fhk,-ℓ amplitudes which led initially to a false prediction of space group symmetry.
KW - Frustrated chain packing
KW - Isotactic polypropylene
KW - β-polymorphic form
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U2 - 10.1016/S0032-3861(97)10160-4
DO - 10.1016/S0032-3861(97)10160-4
M3 - Article
AN - SCOPUS:0032324584
SN - 0032-3861
VL - 39
SP - 6331
EP - 6337
JO - polymer
JF - polymer
IS - 25
ER -