Crystallographic structures on the sequential copolymer of epsilon-caprolactam and pyrrolidinone (nylon 4/6)

The structure and morphology of lamellar crystals of a sequential copolymer of poly(pirrolidinone) with poly(epsilon-caprolactam) (nylon 4/6 copolymer ) has been studied by transmission electron microscopy, electron diffractio n and X-ray diffraction. The results obtained indicate that at room tempera ture single crystals of this copolymer have an alpha-form structure which i s also the most stable one for both related homopolymers. The crystallograp hic unit cell is monoclinic with a = 9.60 Angstrom, b (chain axis) = 14.80 Angstrom, c = 8.06 Angstrom and beta = 67 degrees. The effects of temperatu re on the lattice spacings show that the characteristic 200 and 002 equator ial spacings converge with increasing temperature but do not meet prior to the melting temperature. In conclusion, the copolymer and the related homop olymers behave similarly with respect to their room temperature most stable crystal structure and behavior on heating. The second characteristic cryst alline phase (gamma-form) reported for even nylons could only be obtained b y treating the polymer sample with iodine-potassium iodide solutions. (C) 1 999 Elsevier Science Ltd. AU rights reserved.