Effect of iodine on small‐angle X‐ray diffraction from drawn poly(ethylene terephthalate) film

The effect of iodine sorption on the small‐angle x‐ray diffraction intensity is discussed in terms of the distribution of iodine sorbed in the amorphous regions of polymers. The change in the intensity of the peak corresponding to long periods is measured as a function of the iodine uptake in drawn, and annealed poly(ethylene terephthalate) films. A linear relation with slope K is observed between the square root of relative intensity and iodine uptake. The slope K varies with annealing conditions. Theoretical values calculated for models of the distribution of iodine in amorphous regions, are compared with the observed K. Results can be interpreted on the basis of a “concave” distribution of iodine, i.e., with sorption sites more numerous near a crystal surface than in the interior of an amorphous region.