Polarized Infrared Studies of Amorphous Orientation in Polyethylene and Some Ethylene Copolymers

摘要

Measurements were made of the dichroic ratios of a number of infrared bands for uniaxially deformed low-density polyethylene. In order to characterize the amorphous orientation in the polymer, orientation functions were derived from the results on the conformationally sensitive amorphous bands at 1368/cm, 1352/cm, 1303/cm and 1078/cm. In conjunction with x-ray data and infrared dichroism data on the crystalline 1894/cm band, amorphous orientation functions were also derived from the 2016/cm band which appears to contain a normal amorphous component. The results indicate that extended trans sequences in the amorphous phase orient to a larger extent than isolated trans bonds flanked by gauche bonds. Results on the bands at 720 and 730/cm appear to show discrepancies when compared with the data from the other bands, and possible reasons for this apparent inconsistency are suggested. Amorphous orientation functions have also been derived from the CN stretching band at 2250/cm in a copolymer of ethylene and (2 weight percent) acrylonitrile. The bands at 2016/cm and 1894/cm were also analyzed for this copolymer, in addition to a C = O stretching band at 1740/cm due, apparently to thermal oxidation. Infrared dichroism results are also discussed for a copolymer of ethylene and (4.1 mole percent) methacrylic acid in which 70% of the -COOH groups are neutralized with sodium hydroxide. (Author)