Investigation of solid state imidization reactions of the vapour deposited azo-polyimide thin films by FTIR spectroscopy

In this paper solid state imidization reactions of azo-polyimide thin films prepared at different temperatures have been investigated by FTIR spectroscopy. The starting precursors DAAB (4,4'-diaminoazobenzene) and PMDA (pyromellitic dianhydride) were vacuum deposited as thin films. It was estimated that the necessity of the following thermal treatment 1 h at 300 degrees C are appropriate conditions for imidization of the initial PMDA-DAAB mix to Azo-PI (azo-polyimide) film. The parameters have been selected experimentally (temperatures, deposition rates, mode of substrates, etc.), for the vapour deposition of the precursors in view to prepare layers with a high imidization degree, reproducible composition and structure, which determined the film properties. Due to their magnetic anisotropy and cis-trans-cis isomerization cycle the azo-polymer films are promising material for application in optics, optoelectronics, sensors, etc. For this reason a study of the kinetics of solid state imidization reactions at different temperatures is carried out. It is identified and discussed that the imide III band intensity at 1363-1381 cm(-1) characterizing imide ring is different at three temperatures. (C) 2014 Elsevier B.V. All rights reserved.