Effect of copolymerization on the crystalline structure of polyacrylonitrile

X-ray diffraction of polyacrylonitrile (PAN), poly-2-hydroxyethyl methacrylate (poly-HEMA) and their random copolymers containing low proportions of HEMA has been carried out in order to investigate the changes in the PAN structure produced by introducing some HEMA units into the chain. Both crystalline and amorphous phases were distinguishable in PAN and the copolymers. Considerable decrease in crystallinity on copolymerization was found, but not showing any quantitative relationship with the HEMA content. The crystalline lattice in the copolymers remained similar to that of PAN. A two-phase (crystalline and amorphous) structure of PAN was found more suitable to explain the results.