| Abstract: | The condensation polymerization of 4,4′‐oxydianiline with pyromellitic dianhydride for the formation of poly(amic acid) and the subsequent imidization for the formation of polyimides were investigated for films prepared with vapor‐deposition polymerization techniques. Fourier transform infrared spectroscopy, thermal analysis, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of films at different temperatures indicated that additional solid‐state polymerization occurred before imidization. The experiments revealed that, upon vapor deposition, poly(amic acid) oligomers formed that had a number‐average molecular weight of about 1500 Da. Between 100–130 °C, these chains underwent an additional condensation reaction and formed slightly higher molecular weight oligomers. Calorimetry measurements showed that this reaction was exothermic enthalpy of reaction (ΔH) ～ ?30 J/g] and had an activation energy of about 120 kJ/mol. The experimental ΔH values were compared with results from ab initio molecular modeling calculations to estimate the number of amide groups formed. At higher temperatures (150–300 °C), the imidization of amide linkages occurred as an endothermic reaction (ΔH ～ +120 J/g) with an activation energy of about 130 kJ/mol. The solid‐state kinetics depended on the reaction conversion as well as the processing conditions used to deposit the films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5999–6010, 2004 |
