https://doi.org/10.1351/goldbook.V06628

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.*Source: *

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

Purple Book, 1