Crystal structure of the γ‐form of nylon 6

Abstract

Abstract The crystal structure of the γ‐form of nylon 6 (polycaproamide) obtained by the iodine treatment of the α‐from of nylon 6 has been determined by x‐ray diffraction. The unit cell contains four repeating units \documentclass{article}\pagestyle{empty}\begin{document}$ [\rlap{--} ({\rm CH}_2 \rlap{--})_5 {\rm CONH \hbox{---}}] $\end{document} and is monoclinic with a = 9.33 A., b = 16.88 A. (fiber axis), c = 4.78 A., β = 121°. The space group is P2 1 / a . There is considerable deviation from the planar configuration in the amide group of the chain. The plane of the CH 2 chain zigzag lies nearly parallel to the (00 1 ) plane. The crystal is composed of the pleated sheets of the parallel chains joined by hydrogen bond between the adjacent chains. The chain directions are opposite in alternating sheets. The hydrogen‐bond length is 2.83 A., a reasonable figure for an NH·. O chains joined by a hydrogen bond between the adjacent chains. The direction of the hydrogen bond makes an angle of 12° with the ( 1 00) plane, and the CO and NH bonds are nearly colinear. The amide groups lie at the same level in the cell.