Structural changes in α → γ phase transformations of polycaprolactam

The transition from the to the modification of polycaprolactam caused by treatment with iodine was studied by means of X-ray diffraction. The measurements were carried out on foils with a plane texture. During treatment with aqueous solutions of LiI₃, NaI₃, KI₃ and RbI₃ stable iodine complexes of polycaprolactam were produced. These complexes have a three-dimensional, not quite ordered structure and are similar to one another. Their unit cell has the dimensionsa=15,5 å,b=4,4 å,c=24,7 å; the edges of the unit cell are perpendicular to one another. The iodine forms in the complexes columns that are parallel to the polycaprolactam chains which are arranged into planes parallel to the plane of the foil. The action of water causes the complexes to disintegrate and when the iodine is completely eliminated from the foil the modification of polycaprolactam, which has an equally perfect texture as the initial modification, is formed.In conclusion, the author would like to thank Dr. K. Toman, Dr.Sc., for guiding the work and Ing. B. Sedláek, Dr.Sc., for his interest.