Figure 6 shows the X-ray diffractio

Figure 6 shows the X-ray diffraction profiles of precursor polyimide and thermally rearranged polybenzoxazole membranes. A broad amorphous halo was observed for all the samples, proving the amorphous nature of all these polymers. As shown in Figure 6, the different cross-linking degree for XHPI samples hardly changed the position of the amorphous halo maximum at around 16° (2θ), corresponding to a preferential intersegmental distance of about 0.55 nm (see Table 3), as compared to HPI uncross-linked sample, although the patterns differed slightly in both shape and width of the halo.