Thermodynamically, the excess chemical potential of mixing between a polymer and a theta solvent is zero.
Real polymer coils are more closely represented by a self-avoiding walk because conformations in which different chain segments occupy the same space are not physically possible.
If a solvent is precisely poor enough to cancel the effects of excluded volume expansion, the theta (θ) condition is satisfied.
This makes experimental determination of important quantities such as the root mean square end-to-end distance or the radius of gyration much simpler.
Thermodynamically, the excess chemical potential of mixing between a theta solvent and a polymer is zero.
[vague] One cannot measure the chemical potential by any direct means, but one can correlate it to the solution's osmotic pressure (
The change in the chemical potential when the two are mixed has two terms: ideal and excess: The second virial coefficient, B, is proportional to the excess chemical potential of mixing: B reflects the energy of binary interactions between solvent molecules and segments of polymer chain.
Similar relationships exist for other experimental techniques, including light scattering, intrinsic viscosity measurement, sedimentation equilibrium, and cloud point titration.