Effect of H+ and N+ Irradiation on Structure and Permeability of the Polyimide Matrimid®

This paper presents a comparison of the impact of H+ and N+ ion irradiation on the chemical structure, microstructure, and gas permeation properites of the polyimide, Matrimid. While irradiation with both ions resulted in evolution of chemical structure with loss of functional groups and crosslink formation, there was greater modification of polyimide structure following N+ irradiation at similar total deposited energy. Irradiation with N+ resulted in simultaneous large increases in permeance and permselectivity at comparatively low ion fluences or irradiation time. For example, irradiation at 41014N+/cm2 resulted in a 2.5 fold increase in He permeance with a selectivity of He/CH4 of 340. Much higher H+ fluences were required to achieve similar total deposited energy and combined increases in permeance and permselectivity. The larger modification in chemical structure and gas permeation properties following N+ irradiation was attributed to the relatively large energy loss and damage from the nuclear energy relative to electronic energy loss.