14217 IUPAC Gold Book - anticlined stems 10.1351/goldbook.14217 14217 current 1 Stems in a crystal having opposite side-group orientations with respect to the chain axis (see (a) in figure).(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. Anticlined stems occur in crystalline poly-α-olefins, and also in regioregular poly(3-alkylthiophenes), polyphosphazenes, and polysiloxanes. antidirectional packing https://goldbook.iupac.org//terms/view/14218 directional chain https://goldbook.iupac.org//terms/view/14207 isoclined stems https://goldbook.iupac.org//terms/view/14222 isodirectional packing https://goldbook.iupac.org//terms/view/14223 PAC, 2011, 83, 1831. 'Definitions of terms relating to crystalline polymers (IUPAC Recommendations 2011)' on page 1844 (https://doi.org/10.1351/PAC-REC-10-11-13) https://goldbook.iupac.org/terms/view/14217/html https://goldbook.iupac.org/terms/view/14217/json https://goldbook.iupac.org/terms/view/14217/plain 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. 10.1351/goldbook.14217 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-06-07T03:20:30+00:00