Powder X-ray diffraction of PEI residues were analyzed using a Bragg-Brentano Diffractometer setup having a CuKα (1.54 Å) source on a BRUKER D8 Discover and a LYNXEYE detector. All data (except for PEI = 2°-60°) were collected in the range of 3°-60° 2θ. The scattering vector q and d-spacing values were calculated using the following equations: