Molecular orientation of polymer chains of poly(ethylene 2,6-naphthalate) determined using Mueller matrix infrared spectroscopic ellipsometry supported by density functional theory calculations

Abstract Biaxially oriented semicrystalline film of poly(ethylene 2,6-naphthalate) was investigated via mid-infrared Mueller matrix spectroscopic ellipsometry using a prototype instrument with a quantum-cascade laser as the source. The results were analyzed using a biaxial anisotropic model, and the absorption features are characteristic of the α phase of poly(ethylene 2,6-naphthalate). A comparison with density functional theory calculations of methyl ethyl 2,6-naphthalate, a model molecule consistent with the structure and conformation of α -poly(ethylene 2,6-naphthalate), reveals that the planes of naphthalene moieties of the polymer backbone are parallel to the surface. A parameterized model of the biaxial dielectric function is reported.