Term: expansion factor
https://doi.org/10.1351/goldbook.E02270

Definition:
The ratio of a dimensional characteristic of a macromolecule in a given solvent at a given temperature to the same dimensional characteristic in the θ state at the same temperature. The most frequently used expansion factors are: expansion factor of the mean-square end-to-end distance, αr = sqrt(/o); expansion factor of the radius of gyration αs = sqrt(/o); viscosity expansion factor αη = ([η]/[η]θ)1/3 where [η] and [η]θ are the intrinsic viscosity in a given solvent and in the θ state at the same temperature, respectively. Expansion factors defined by different dimensional characteristics are not exactly equal, nor need they have a constant ratio as a function of relative molecular mass.

Related Terms:
1) radius of gyration (http://doi.org/10.1351/goldbook.R05121).
2) viscosity (http://doi.org/10.1351/goldbook.V06627).
3) relative molecular mass (http://doi.org/10.1351/goldbook.R05271).

Source: Purple Book, 1st ed., p. 59 (http://old.iupac.org/publications/books/author/metanomski.html)

Citation: 'expansion factor' 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.E02270

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