Term: viscosity function, \(\mathit{\Phi}\)
https://doi.org/10.1351/goldbook.V06628

Definition:
A coefficient connecting the intrinsic viscosity, the radius of gyration and the molar mass of a chain macromolecule, according to the equation: \[\text{[}\eta \text{]} = \frac{\mathit{\Phi }\ 6^{3/2}\ ( < s^{2} > )^{3/2}}{M}\] where [η] is the intrinsic viscosity, s is the radius of gyration and M is the molar mass. The viscosity function is often referred to as the Flory constant.

Related Terms:
1) coefficient (http://doi.org/10.1351/goldbook.C01124).
2) viscosity (<em>of a polymer</em>) (http://doi.org/10.1351/goldbook.V06627).
3) radius of gyration (<em>of a polymer</em>) (http://doi.org/10.1351/goldbook.R05121).
4) intrinsic viscosity (<em>of a polymer</em>) (http://doi.org/10.1351/goldbook.I03140).

Source: Purple Book, 1st ed., p. 64 (http://old.iupac.org/publications/books/author/metanomski.html)

Citation: 'viscosity function, \(\mathit{\Phi}\)' 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.V06628

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.

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.