Production of polyamic acid in supercritical carbon dioxide with N,N‐dimethylformamide

Abstract

To develop a microscale processing technique for aromatic polyimides (APIs) in supercritical carbon dioxide (scCO 2 ), the relationships between the polymerization condition, the phase behavior during polymerization and the molecular weight of polyamic acid (PAA)-an intermediate in the production of polyimides-were investigated in scCO 2 at 50 C. 4,4 0 -Diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA) were used as monomers of aromatic diamine and tetracarboxylic dianhydride, respectively, and 19 mol % of N,N-Dimethylformamide (DMF) was added to scCO 2 as a cosolvent. The cloudy phase appeared immediately when ODA and PMDA were mixed under any experimental conditions. However, the appearances of the phase behaviors during polymerization differed depending on the polymerization pressure and the initial monomer concentration. The number average molecular weight of PAA increased as the monomer concentration was increased in scCO 2 , as was the case with polymerization in pure DMF at atmospheric pressure, despite differences in the phase behavior. On the other hand, the weight average molecular weight of PAA depended on the phase behaviors during polymerization along with the monomer concentration. Moreover, API obtained from the PAA synthesized in scCO 2 was analyzed using a Fourier transform infrared spectrophotometer and thermogravimetric analyzer, and the results were compared with those of APIs obtained by the solution polymerization. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39878.

Effect of molecular rigidity and hydrogen bond interaction on mechanical properties of polyimide fibers

“…Gel permeation chromatography (GPC) is a direct method to determine the molecular weight of PAA, while the intrinsic viscosity of polyamic acid is a simple and effective method to characterize the molecular weight indirectly. In this article, we choose intrinsic viscosity of polyamic acid to compare the molecular weight.…”

Phase appearance during polymerization of fluorinated polyimide monomers and deposition into the microscopic‐scale trenches in supercritical carbon dioxide

“…21 Therefore, only the procedure of the experiment is briefly described here. First, a high-pressure cell (Toyo Koatsu, an internal diameter of 10 mm and an internal volume of 17.1 cm 3 ) equipped with Pyrex windows for visual observation was heated to the experimental temperature using cartridge heaters.…”

“…The details of the GPC analysis method, including information concerning the columns that were used, are described in a previous paper. 21 Apparatus and Procedure for Deposition into Microscopic-scale Trenches in scCO 2 An apparatus for the deposition of PI was developed in a previous study. 23 This apparatus was based on the flow method, which consists of two supply lines for each monomer dissolved in scCO 2 with DMF as a cosolvent and a cold-wall-type deposition reactor (Toyo Koatsu, 100 mL of internal volume) located in a thermostatic air bath.…”

“…The FT-IR spectra of these are described in Figure 7. The vibrational modes that were focused on were the C@O stretching found at 1540 and 1650 cm 21 for PAA, 25,26 as well as the CAN stretching, C@O symmetric stretching, and C@O asymmetric stretching at 1360, 1730, and 1790 cm 21 , respectively, for PI. 8,[25][26][27][28] The figure shows that the spectrum of the deposited film was similar to the reference PI.…”

New High-Performance Materials: Bio-Based, Eco-Friendly Polyimides

“…At the same time, the employment of scCO2 in the synthesis of polymers leads to a small decrease in the Tg and dielectric constant values, due to a plasticizing effect. This can be an important advantage when it comes to the processability possibilities of the final material [79][80][81][82].…”