anticlined stems

https://doi.org/10.1351/goldbook.14217
Stems in a crystal having opposite side-group orientations with respect to the chain axis (see (a) in figure).
anticlined stems

(a) Pairs of anticlined stems and (b) pairs of isoclined stems of regioregular poly(3-butylthiophene), i.e., poly(3-n-butylthiophene-2,5-diyl). Since regioregular poly(3-n-butylthiophene-2,5-diyl) is also a directional chain, (a) is an example of antidirectional packing of two chains, while (b) is an example of isodirectional packing.

Note: Anticlined stems occur in crystalline poly-α-olefins, and also in regioregular poly(3-alkylthiophenes), polyphosphazenes, and polysiloxanes.
Source:
PAC, 2011, 83, 1831. (Definitions of terms relating to crystalline polymers (IUPAC Recommendations 2011)) on page 1844 [Terms] [Paper]
Citation: 'anticlined stems' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.14217 RIS BibTex EndNote
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