{"term":{"id":"09625","title":"number of pseudo-generations","longtitle":"IUPAC Gold Book - number of pseudo-generations","doi":"10.1351\/goldbook.09625","code":"09625","status":"current","definitions":[{"id":1,"text":"Number of generations of the hypothetical dendrimer molecule that would present the same ratio of constitutional repeating units to core unit.","notes":{"1":"The number of pseudo-generations can be a decimal number, while the number of generations of a dendrimer molecule is an integer.","2":"In hyperbranched polymers obtained by the \\({\\rm{AB}}_{x}\\mbox{-}\\rm{type}\\) monomer + \\({\\rm{B}}_{y}\\mbox{-}\\rm{type}\\) monomer polycondensation approach, where \\(\\rm{A}\\) and \\(\\rm{B}\\) represent mutually reactive groups, the number of pseudo-generations \\(n\\) can be calculated by solving the equation: \\[r = y(x^n - 1)\/(x - 1)\\], where \\(r\\) is the mole ratio of \\({\\rm{AB}}_{x}\\mbox{-}\\rm{type}\\) monomer to \\({\\rm{B}}_{y}\\mbox{-}\\rm{type}\\) monomer in the initial monomer mixture. See the figure for an example of \\({\\rm{AB}}_2\\) and \\({\\rm{B}}_{3}\\mbox{-}\\rm{type}\\) monomers (\\(x = 2\\) and \\(y = 3\\)). Idealized representation of an aliphatic hyperbranched polyester macromolecule obtained by one-step bulk polyesterification of 3-hydroxy-2-(hydroxymethyl)-2-methylpropanoic acid (\\({\\rm{AB}}_{2}\\mbox{-}\\rm{type}\\) monomer) and 2-ethyl-2-(hydroxymethyl)propane-1,3-diol (\\({\\rm{B}}_{3}\\mbox{-}\\rm{type}\\) molecule). ","3":"The use of the terms generation and number of generations for a hyperbranched polymer is not acceptable."},"contexts":[],"links":[{"term":"core unit","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/09603"},{"term":"dendrimer molecule","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/09605"},{"term":"generation","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/09614"},{"term":"hyperbranched polymers","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/09618"},{"term":"number of generations","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/09624"}],"sources":["PAC, 2019, 91, 523. 'Nomenclature and terminology for dendrimers with regular dendrons and for hyperbranched polymers (IUPAC Recommendations 2017)' on page 533 (https:\/\/doi.org\/10.1515\/pac-2016-1217)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/09625\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/09625\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/09625\/plain"},"citation":"Citation: 'number of pseudo-generations' 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.09625","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":"2026-07-15T06:16:28+00:00"}}