viscosity function, \(\mathit{\Phi}\)
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.
Purple Book, 1st ed., p. 64 (