Mechanical relaxation of Poly-4-methyl-pentene-1 at cryogenic temperatures

In the temperature dispersion curve of poly-4-methyl-pentene-1 (P4MP1), the secondary absorption associated with thermal motion of side chains (βsc) can be observed at about −150 to −160°C (110 cps) as a doublet. By inspecting the absorptions of the various kinds of samples with different crystallinity, including bulk-crystallized and solution-grown crystals, the low-temperature secondary absorption can be separated into the βsc-A absorption associated with the frozen amorphous chains and the βsc-C absorption associated with the defect region within the crystal phase. The fraction of the defect region, A′, can be evaluated from the absorption magnitude of the βsc-C absorption by use of the corresponding absorption of the completely amorphous atactic samples as a reference. When the secondary absorptions of the bulk-crystallized samples are compared with those of the solution-grown crystals with the same crystallinity, the A′ region of the solution-grown crystals is less than that of the bulk-crystallized ones. Under the assumption that the A′ region can be ascribed to the lateral region surrounding each mosaic crystal composing a lamella, the edge length of the mosaic crystal amounts to about 160 Å for the single crystal of P4MP1 prepared from the xylene solution at 60°C. The effect of crystal transformation, y-ray irradiation, and annealing of single crystals upon the γsc absorption has also been surveyed.