{"term":{"id":"12740","title":"alpha relaxation","longtitle":"IUPAC Gold Book - alpha relaxation","doi":"10.1351\/goldbook.12740","code":"12740","status":"current","synonym":"<em>synonym<\/em>: α-relaxation","definitions":[{"id":1,"text":"Highest-temperature or lowest-frequency relaxation in the loss curve of a polymer.","notes":{"1":"The \\(\\upalpha\\)-relaxation is commonly related to cooperative conformational changes in macromolecules. These changes typically involve \\(\\pu{10\\!-\\! 20}\\) main-chain atoms. For a polymer in a glassy state, the \\(\\upalpha\\)-relaxation is characteristic of the glass transition.","2":"For some partially crystalline polymers, for example, polyethylene or polyoxymethylene, the \\(\\upalpha\\)-relaxation originates from motions within the crystalline regions (the so-called \"crystalline relaxation\"). In such cases, the β-relaxation usually corresponds to the glass transition."},"links":[{"term":"glassy state","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/12774"},{"term":"loss curve","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/12781"},{"term":"β-relaxation","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/12744"}],"sources":["PAC, 2013, 85, 1017. 'Glossary of terms relating to thermal and thermomechanical properties of polymers (IUPAC Recommendations 2013)' on page 1018 (https:\/\/doi.org\/10.1351\/PAC-REC-12-03-02)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/12740\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/12740\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/12740\/plain"},"citation":"Citation: 'alpha relaxation' 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.12740","license":"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.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"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.","accessed":"2026-07-15T03:09:36+00:00"}}