The equilibrium phase diagram of mixtures of linear poly(2-phenoxyethylacrylate) of molecular weight M-w = 181 000 g/mol, and the low molecular weight liquid crystal 4-cyano-4'-n-pentyl-biphenyl known as 5CB has been established using polarized optical microscopy and differential scanning calorimetry (DSC). The diagram exhibits an upper critical solution temperature and three main transitions: crystalline + isotropic (C + I) to nematic + isotropic (N + I), (N + I) to isotropic + isotropic (I + I), and (I + I) to isotropic (I). The (C + I) to (N + I) transition is observed by DSC, while the (N + I) to (I + I) transition is detected by optical microscopy and DSC, and the (I + I) to (I) transition only by optical microscopy. The results were successfully analyzed within a theoretical model combining the Flory-Huggins lattice theory for isotropic mixing and the Maier-Saupe theory of nematic ordering.