Title: long period
Long Title: IUPAC Gold Book - long period
DOI: 10.1351/goldbook.14251
Status: current

Definition
Average periodicity (repeating distance) of the layers of lamellar crystals in a stacked assembly.

Note
The long period is usually measured by SAXS (small-angle X-ray scattering), SANS (small-angle neutron scattering), atomic force microscopy (AFM), or transmission electron microscopy (TEM), and is the sum of the average thickness of the lamellar crystals and the average thickness of the amorphous inter-lamellar region.

Source
- PAC, 2011, 83, 1831. 'Definitions of terms relating to crystalline polymers (IUPAC Recommendations 2011)' on page 1855 (https://doi.org/10.1351/PAC-REC-10-11-13)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/14251/html
- json: https://goldbook.iupac.org/terms/view/14251/json
- xml: https://goldbook.iupac.org/terms/view/14251/xml

Citation: Citation: 'long period' 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.14251
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Accessed: 2026-08-05T17:27:51+00:00