Study of anisotropic optical properties of poly(arylenephenylene) thin films: Dependence on polymer backbone

The correlation between the optical properties and microstructural parameters of different poly(arylenephenylene) thin films, deposited by spin-coating, is investigated by spectroscopic ellipsometry. Conjugated polymer films are found to be anisotropic. They are birefringent, with a higher refractive index in the plane of the film than perpendicular to it. This anisotropy is due to a preferential in-plane orientation of the polymer chains. The dependence of both the in-plane and out-of-plane optical constants of the polymeric thin films and of the fundamental pi-pi* transition on the structure of the chain backbone are studied. The change of the pi-pi* transition energy of the polymers from solution to thin film and its correlation with the molecular structure are investigated as indicative of interchain interactions.