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isomorphous structures

in polymers

Also contains definition of: enantiomorphous structures in polymers

In the crystalline state, polymer chains are generally parallel to one another but neighbouring chains of equivalent conformation may differ in chirality and/or orientation. Chains of identical chirality and conformation are isomorphous. Chains of opposite chirality but equivalent conformation are enantiomorphous. For example, two ...TG+TG+TG+... helices of isotactic poly(propylene) are isomorphous. Isotactic poly(propylene) chains of the ...TG+TG+TG+... and ...GTGTGT... types are mutually enantiomorphous. With regard to orientation, consider a repeating side group originating at atom A 1 i, the first atom of the side group being B α i. For certain chain symmetries (helical, for instance) the bond vectors b → A 1 i B α i have the same components (positive or negative) b → · c → | c → | along the c axis for every i.
I03299
Two equivalent (isomorphous or enantiomorphous) chains in the crystal lattice, having identical components of the bond vectors along c, both positive or both negative, are designated isoclined; two equivalent chains having bond vectors along c of the same magnitude but opposite sign are designated anticlined.
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IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook.
Last update: 2014-02-24; version: 2.3.3.
DOI of this term: doi:10.1351/goldbook.I03299.
Original PDF version: http://www.iupac.org/goldbook/I03299.pdf. The PDF version is out of date and is provided for reference purposes only. For some entries, the PDF version may be unavailable.
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