Fourier transform infrared spectroscopic analyses of 2,6 diethylaniline monomer and plasma polymerized 2,6 diethylaniline (PPDEA) thin films reveal that structural rearrangement/cross-linking have occurred in the chemical structure of formed thin films due to plasma polymerization process. However, the aromatic ring structure and the ethyl group of the starting monomer are retained in PPDEA thin film. The optical band gaps (E-g) of the PPDEA thin films of different thicknesses were found to be about 3.60 and 2.23 to 2.38 eV for direct and indirect transitions respectively. The change in Eg values with thickness is, due to increased structural modification in PPDEA with plasma duration. The Urbach energy, steepness parameter and extinction coefficient are also assessed for the PPDEA thin films of different thicknesses from ultraviolet-visible spectroscopic data. (C) 2013 Elsevier B. V. All rights reserved.