12264 IUPAC Gold Book - Flory–Fox assumption 10.1351/goldbook.12264 12264 current 1 Assumption that the Kirkwood–Riseman theory can be applied to linear isolated macromolecules in solution, independent of whether they are in the theta state. The Kirkwood–Riseman relationships between \(r_{D}\) and \(r_{\eta}\) and the root-mean-square radius of gyration, \(\lt\!s^{2}\!\gt\), are then \[r_{D} = 0.675 \lt\!s^{2}\!\gt^{1/2} = 0.675 \lt\!s_{\circ}^{2}\!\gt^{1/2} \alpha_{D}\] and \[r_{\eta} = 0.256 \lt\!s^{2}\!\gt^{1/2} = 0.256 \lt\!s_{\circ}^{2}\!\gt^{1/2} \alpha_{\eta}\] where \(r_{D}\) and \(r_{\eta}\) are the equivalent hydrodynamic radii in translational diffusive flow and viscous flow, and \(\alpha_{D}\) and \(\alpha_{\eta}\) are the corresponding expansion factors. Kirkwood–Riseman theory https://goldbook.iupac.org//terms/view/12263 equivalent hydrodynamic radii https://goldbook.iupac.org//terms/view/12258 root-mean-square radius of gyration https://goldbook.iupac.org//terms/view/12191 PAC, 2015, 87, 71. 'Definitions of terms relating to individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers (IUPAC Recommendations 2014)' on page 104 (https://doi.org/10.1515/pac-2013-0201) https://goldbook.iupac.org/terms/view/12264/html https://goldbook.iupac.org/terms/view/12264/json https://goldbook.iupac.org/terms/view/12264/plain Citation: 'Flory–Fox assumption' 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.12264 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. 2026-04-18T06:49:16+00:00