12263 IUPAC Gold Book - Kirkwood–Riseman theory 10.1351/goldbook.12263 12263 current 1 Theory, based on the pearl-necklace model, that describes the translational diffusive and viscous flows of an isolated linear macromolecule in solution in the theta state and accounts for the gradual change from free-draining behaviour at lower molecular weights to impermeable behaviour at higher molecular weights. The Kirkwood–Riseman theory is usually applied in the impermeable limit when it essentially relates the equivalent hydrodynamic radius to the root-mean-square unperturbed radius of gyration, \(\lt\!s_{\circ}^{2}\!\gt\), with \[r_{D} = 0.675 \lt\!s_{\circ}^{2}\!\gt^{1/2}\] and \[r_{\eta} = 0.256 \lt\!s_{\circ}^{2}\!\gt^{1/2}\] where \(r_{D}\) and \(r_{\eta}\) are the equivalent hydrodynamic radii in translational diffusive flow and viscous flow. equivalent hydrodynamic radius https://goldbook.iupac.org//terms/view/12258 free-draining https://goldbook.iupac.org//terms/view/12254 impermeable https://goldbook.iupac.org//terms/view/12255 pearl-necklace model https://goldbook.iupac.org//terms/view/12262 root-mean-square unperturbed radius of gyration https://goldbook.iupac.org//terms/view/12193 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/12263/html https://goldbook.iupac.org/terms/view/12263/json https://goldbook.iupac.org/terms/view/12263/plain Citation: 'Kirkwood–Riseman theory' 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.12263 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. 2026-04-18T08:20:57+00:00