Equilibrium phase diagram of poly(2-phenoxyethylacrylate) and 5CB

The equilibrium phase diagram of mixtures of linear poly(2-phenoxyethylacrylate) of molecular weight Mw=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.