Surface characterization of soluble polyimide by inverse gas chromatography

Inverse gas chromatography ( IGC) is a new characterizing method for surface properties in polymer field.The main difference between GC and IGC is that the interested species is the polymer material acting as the stationary phase in IGC column. Probe solvents with known properties are injected in column. For the interactions between probe solvents and polymer stationary phase are different, the surface properties of polymer can be determined from the retention volume of probe solvents. In this work, surface properties of soluble polyimide HQDPA-DMMDA were quantitatively analyzed by the IGC method. Four n-alkanes ( C-6, C-7, C-8 and C-9) were chosen as non-polar probes to characterize the dispersive component of free energy. Trichloromethane ( CHCl3), ethyl ether and acetone were chosen as polar probes to detect the Lewis acid-base parameters. It was found the dispersive component of free energy of HQDPA-DMMDA was 34.37 mJ/m(2), 31.80 mJ/m(2), 29.50 mJ/m(2) and 27.64 mJ/m(2) at 50 degrees C, 60 degrees C, 70 degrees C and 80 degrees C, respectively. The surface free energy decreased linearly with increasing temperature. The Lewis acidic number K-a of HQDPA-DMMDA was 0.4115, and basic number K-b was 0.5812. The result meant that HQDPA-DMMDA was a weak Lewis amphoteric polymer.