Electron spin resonance studies of spin-labelled polymers—VIII: Relaxation processes in low density polyethylene

✍ Scribed by A.T. Bullock; G.G. Cameron; P.M. Smith

• Publisher: Elsevier Science
• Year: 1975
• Tongue: English
• Weight: 664 KB
• Volume: 11
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(75)90053-1

✦ Synopsis

Low density polyethylene was spin-labelled with an oxazolidine-N-oxyl group. Correlation times for the motion of the label were calculated both in the slow-motion region and in the motionallynarrowed region. In the latter situation, the central line shape was successfully simulated. A correlation map revealed the :t-and fl-relaxation processes in solid polyethylene, with activation energies of 48 and 28 kJ mol-~, respectively. The segmental reorientation processes of polyethylene in the melt and in solution had activation energies of 15.2 and 22'9 kJ tool-1, respectively. Taking into account the effect of viscous drag of the solvent, the two activation energies were almost the same suggesting that the same relaxation process occurs in the bulk molten polymer and in the isolated molecule. The model compound 2,2',5,5'-tetramethyl-3-oxazolidinyloxy was synthesized and used as a spin-probe in the polymer. The spin-probe experiments gave a transition temperature attributed to the ),-relaxation.