Preparation and shallow trap level distribution of polyimide

The pure PI of benzene type film has been prepared by two steps dispersion polymerization process. The thermally stimulated current method was used to investigate the charge carrier trap levels of pure PI films which consist of self-made, 3M and dupont PI films. The results show that the temperature of the peak and trap level of 3M PI films is higher than that of other γ peak. Its higher trap energy level is attributed to the high degree of polymerization, which lead to higher energy for the movement of chain. Improving the viscosity of polyamide properly in the process of preparing PI is helpful for the polymerization of the film and the improvement of the film performance. The β peak temperature of 3M and DuPont PI films is about 35 K higher than that of homemade PI films. It is also a high degree of polymerization of 3M and DuPont pure PI films, resulting in difficulties in parenchymal movement. The β peak is related to dipole orientation relaxation and the β peak temperature is about 345 K for amorphous PI, which is smaller than the glass transition temperature. At this temperature, the movement of macromolecular chain is difficult and only the polar group such as carbonyl can move group. Only DuPont PI has the α_C peak which is related to the movement of crystal regions and interface effect.