INFRARED DICHROIC STUDIES ON ORIENTATION OF LABELED MOLECULES IN UNIAXIALLY AND BIAXIALLY DRAWN GELATION CRYSTALLIZED ULTRAHIGH MOLECULAR-WEIGHT POLYETHYLENE

Orientation of labelled molecules in uniaxially and biaxially drawn ultrahigh molecular weight polyethylene (UHMWPE) films has been characterized by means of infrared dichroism. Both deuterated UHMWPE and deuterated high density polyethylene (d-HDPE) were used as labelled molecules, The polymer concentration of deuterated species was 1 wt% to avoid possible polymer phase separation. These deuterated polymers were mixed with protonated UHMWPE by co-dissolving in decalin at an elevated temperature. Upon lowering the temperature, gelation crystallization took place. The gel-films were dried and stretched uniaxially and biaxially to obtain high oriented specimens. The orientation of crystalline chains was determined from 720 and 730 cm(-1) bands, whereas that of the labelled chains was measured from the 2194 and 2088 cm(-1) bands as they are specific to the deuterated species. It turned out that the orientation of deuterated molecules was indistinguishable from those of crystal a- and b-axis in a uniaxial drawing, but deviations were seen in the biaxial stretching, suggesting that the orientation of labelled molecules is not strictly of crystalline origin.