Infrared analysis of brominated polyethylene single crystals

Abstract

. Studies of polyethylene single crystals have yielded considerable information on the nature of the fold surface; however, interpretation of the results for this deceptively simple polymer is still a matter of debate. Selective chemical modification of the surface represents a powerful structural probe which has received little practical attention. The ability to selectively degrade the surface while leaving the crystalline core intact has been used to estimate the length and uniformity of chain segments traversing the Nondestructive halogenation reactions have also been shown to selectively modify the surface," but have not been exploited for surface characterization. In a previous paper, conditions for the suspension bromination of polyethylene were identified and the selectivity of the attack for noncrystalline regions of the polymer was ~o n f i r m e d .~The present investigation concerns the infrared analysis of polyethylene single crystals selectively modified by the nondestructive bromination reaction. Extensive infrared analysis of polyethylene crystals has shown the spectrum to be sensitive to morphological features of the crystalline structure, and the recent advent of Fourier transform infrared instruments wit,h a dedicated minicomputer provides a previously unavailable degree of resolution and capability to digitally manipulate data.

Random, Defect-Free Ethylene/Vinyl Halide Model Copolymers via Condensation Polymerization

“…For RPE15Cl , the peaks at 612 and 664 cm -1 correspond to C−Cl stretching vibrations . Finally, peaks at 537 and 615 cm -1 for RPE15Br correspond to C−Br stretching vibrations . Characteristic peaks at ∼720 and ∼1470 cm -1 , which correspond to vibrational modes of methylene sequences in PE analogues, are also observed for each of the samples.…”

“…16 Finally, peaks at 537 and 615 cm -1 for RPE15Br correspond to C-Br stretching vibrations. 17 Characteristic peaks at ∼720 and ∼1470 cm -1 , which correspond to vibrational modes of methylene sequences in PE analogues, are also observed for each of the samples. For RPE15F, the doublets observed at 729-721 and 1472-1463 cm -1 are the same as observed in orthorhombic crystalline PE.…”

Infrared Spectroscopy and X-ray Diffraction Characterization of Dimorphic Crystalline Structures of Polyethylenes with Halogens Placed at Equal Distance along the Backbone

“…Gauche conformers absorb at higher frequencies. Gauche and trans conformers are easily identified in all the spectra of Cl and Br containing polyethylenes of Figure in reference to extensive past work on ethylene vinyl chloride and ethylene vinyl bromide copolymers. − The C–Cl band at 614 cm –1 corresponds to vicinal trans conformers, and the band at 665 cm –1 is associated with the gauche conformations. Equivalent bands for bromine containing polyethylenes appear at frequencies of 538 cm –1 for trans conformers and at 612 cm –1 for those with the gauche conformation.…”

Precision Ethylene/Vinyl Bromide Polymers

“…[15] From these Scheme 1. data it becomes clear that with increasing bromine content, the ratio of gauche C À Br (~613 cm…”