The method is well established and there are many books and articles on how such calculations should be conducted. But all I can find is works on polymer blends or polymer/drug conjugates and nothing on polymer/solvent systems.
We recently published some work on calculating the Flory-Huggins interaction parameters of short-chain polymethylmethacrylate (PMMA) fragments with the solvents methyl isobutyl ketone (MIBK) and isopropyl alcohol (IPA). You may find this on my profile or on the URL below:
http://dx.doi.org/10.1116/1.4766318
Btw, Phillip Choi's book on Polymer Science and Engineering (2013) also has a chapter on polymer solutions, as does Rubinstein's 2003 book.
we have recent;y published a work on the solubility of P3ATs in THF. We have calculated the FH interaction parameters via model potential molecular dynamics simulations. You will find also a brief summary of the theory behind the method in the Supporting Information.
You can find the paper here: http://dx.doi.org/10.1021/ma401345n