Term: Mark–Houwink equation
https://doi.org/10.1351/goldbook.M03706

Definition:
The equation describing the dependence of the intrinsic viscosity of a polymer on its relative molecular mass (molecular weight) and having the form: \[[\eta] = K\cdot M_{\text{r}}^{a}\] where [η] is the intrinsic viscosity, K and a are constants the values of which depend on the nature of the polymer and solvent as well as on temperature and Mr is usually one of the relative molecular mass averages.

Notes:
0) The use of this equation with the @R05271@ (@M04000@) is recommended, rather than with molar mass (which has the dimension of mass divided by @A00297@), since in the latter case the constant K assumes awkward and @V06600@ dimensions owing to the fractional and @V06600@ nature of the exponent a.
1) Kuhn and Sakurada have also made important contributions and their names are sometimes included, as, for example, in the Kuhn–Mark–Houwink–Sakurada equation.

Related Terms:
1) relative molecular mass (http://doi.org/10.1351/goldbook.R05271).
2) molecular weight (http://doi.org/10.1351/goldbook.M04000).
3) amount of substance (http://doi.org/10.1351/goldbook.A00297).
4) variable (http://doi.org/10.1351/goldbook.V06600).
5) viscosity (<em>of a polymer</em>) (http://doi.org/10.1351/goldbook.V06627).
6) 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: 'Mark–Houwink equation' 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.M03706

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