Plasma polymerized 1, 1, 3, 3-tetramethoxy-propane (PPTMP) thin films of different thicknesses were prepared through glow discharge of 1, 1, 3, 3-tetramethoxypropane using a capacitively coupled reactor. The scanning electron micrographs show that as-deposited PPTMP thin films are smooth, uniform and pinhole free. Infrared spectroscopic investigation indicates the formation of conjugation along with C=O bonds in as deposited PPTMP thin films. Apart from aliphatic conjugation of C=C and C=O bonds there is formation of C-O-C bond owing to rearrangement of oxygen due to heat treatment of PPTMP thin films. A red shift in the maximum absorption wavelength of the ultra violet-visible spectra for all the PPTMP thin films is observed compared to the monomer maximum absorption wavelength. The absorption coefficient, allowed direct transition, E(qd), allowed indirect transition and E(qi), energy gaps were determined. The Eqd and Eqi are found to be about 2.92 to 3.16 eV and 0.80 to 1.53 eV respectively, for as deposited PPTMP samples of different thicknesses. The Eqi of two samples of different thicknesses heat treated at 673 K for 1 hour is 0.55 and 0.65 eV. (C) 2010 Elsevier B.V. All rights reserved.