Anisotropy of spin-probe rotation in poly(vinyl acetate)

✍ Scribed by G.G. Cameron; A.T. Bullock; Isabel S. Miles

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 355 KB
• Volume: 21
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(85)90108-9

✦ Synopsis

A study of the anisotropy of rotation has been carried out, over a wide temperature range, for two nitroxide spin probes 2,2-di-n-butyl-5,5-dimethyl-3-oxazolidinyloxyl (DBOZ) and 2,2-di-n-nonyl-5,5dimethyl-3-oxazolidinyloxyl (DNOZ) in poly(vinyl acetate) (PVAc). Studies of the motion of DBOZ in PVAc plasticized with di-n-butyl phthalate were also conducted. For all systems, the observed behaviour is consistent with axially symmetric rotational diffusion about a particular molecular axis. In PVAc the rotational anisotropy decreases with increasing temperature and is more pronounced for the larger of the two probes, DNOZ. For DBOZ in plasticized PVAc, the energy of activation for probe rotation is greater for rotation perpendicular to the unique axis than for rotation about it. Both energies of activation, particularly the former, increase with increasing polymer concentration. The data indicate that the spin probes tend to be oriented along the unique rotational axis.