The Flory-Huggins theory for the free energy of mixing in isotropic phases, in conjunction with the Maier-Saupe theory for phase transition of a nematic liquid crystal, was applied to a diepoxide-diamine-liquid crystal blend in pre-and post-gel stages. The analysis was performed taking the distribution of polymeric species into account at any conversion level. In the post-gel stage, the elastic energy contribution was included in the free energy expression. Cloud-paint and shadow curves, characteristic of isotropic-isotropic and nematic-isotropic equilibria, were generated in temperature versus composition coordinates covering the whole conversion range. Experimental results for the isotropic-nematic transition could be reproduced by numerical simulation, using an interaction parameter inversely proportional to temperature and decreasing with conversion. The thermodynamic analysis can be used to control the morphologies of polymer dispersed liquid crystals.