STRUCTURE OF ULTRAHIGH-MOLECULAR-WEIGHT POLYETHYLENE IN THE SOLID-STATE AS STUDIED BY VARIABLE-TEMPERATURE C-13 CP MAS NMR-SPECTROSCOPY

In order to obtain some insight into the structure of an ultrahigh‐molecular‐weight polyethylene sample, 13C CP/MAS NMR experiments have been carried out at temperatures from 23 to −108°C. The peak for the crystalline component moves upfield with a decrease in temperature, which is contrary to what was reported previously for a melt‐crystallized polyethylene sample. On the basis of x‐ray diffraction results and quantum‐chemical calculations, it is suggested that the methylene carbons are in the distorted orthorhombic form at low temperatures. Copyright © 1990 John Wiley & Sons, Inc.