Fabrication by Spin-Coating and Optical Characterization of Poly(styrene-co-acrylonitrile) Thin Films

The optical characteristics of poly(styrene-co-acrylonitrile) thin films obtained by spin-coating of polymer blend in tetrahydrofuran were investigated by spectroscopic ellipsometry, spectrophotometry, and atomic force microscopy. Film thickness can be broadly varied by changing the polymer concentration.The film thickness dependence on PSAN concentration shows a non-linear behavior that can be explained by a concentration-dependent viscosity. According to previously proposed models, prepared solutions are close to the concentrated solution regime. Films show a broad transparency range and refractive index independent of film thickness. The refractive index values range from 1.55 to 1.6 in the visible range. Thermal treatment revealed good stability of the films up to 220 °C and a progressive deterioration for larger temperatures, with evident damage at 300 °C. UV-induced photodegradation was observed and results showed a progressive decrease of transmittance in the range between 200 and 300 nm but PSAN thin films show no changes when exposed to light from a solar illuminator. These investigations indicate that PSAN is an excellent candidate for thin film polymer-based optical uses like interference coatings or encapsulation of solar cells.