initiator efficiency

initiation of polymerization
symbols: f, fi
https://doi.org/10.1351/goldbook.08960
Number of growing chains initiated divided by the number of active-centers generated from initiator molecules.
Notes:
  1. The number of growing chains initiated is the number of initiating radicals formed. The number of active centers generated is the number of active centers that could formed be in the absence of any cage effect.
  2. In a radical polymerization, the frequency of production of propagating radicals from an initiator that provides two similar radicals is 2kdfi, where kd is the rate coefficient for initiator decomposition.
  3. In RDP the efficiency of conversion of a starting initiator into a macroinitiator may be called the initiator efficiency (see initialization efficiency).
  4. The initiator efficiency for radical generation from initiators such as dialkyl diazenes and organic peroxides (common symbol f, recommended symbol fg to distinguish from fi) is defined as the fraction of radicals that escape the cage (see cage effect) and are potentially available for reaction with a substrate (e.g., monomer). The value of fi will usually be less than fg as depending on the monomer and the monomer concentration, initiator-derived radicals may react to form products other than initiating radicals.
See also: initialization efficiency
Source:
PAC, 2022, 94, 1093. (Terminology for chain polymerization (IUPAC Recommendations 2021)) on page 1123 [Terms] [Paper]
Citation: 'initiator efficiency' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.08960 RIS BibTex EndNote
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