Enhanced x‐ray diffraction patterns from oriented fibers

The difference x‐ray diffraction pattern can reveal the presence of oriented, ordered material whose conventional diffraction pattern is masked by that of unoriented, disordered material. It is shown that this enhancement results from the fact that scattering from only oriented material contributes to the difference intensity, defined as the difference between the scattered intensity and its average over the polar angle in intensity space. Difference patterns of lightly crosslinked natural rubber, obtained as a function of elongation, show the development of crystallinity at smaller elongations than do the corresponding conventional patterns and indicate that nearly all the oriented material is crystalline. The difference and conventional patterns were obtained from the same diffractometer data. Photographically recorded diffraction patterns are intermediate between the conventional and difference diffractometer patterns in sensitivity to crystallinity. The difference diffraction pattern of a highly oriented atactic polystyrene fiber shows no evidence of crystallinity, the halos on the difference pattern being just as broad as those on the conventional pattern with no apparent tendency to break up into crystalline lines.