NMR and ESR study of the local dynamics in some polyisoprene solutions

The spin-lattice relaxation time T-1 of the protons attached to the polymer ic chain was measured in some polyisoprene-C7D8, polyisoprene-CCl4 and poly isoprene-CDCl3 solutions: over a wide range of the temperature above the gl ass transition temperature. The correlation time tau(c) of the local motion of the polymeric segments, corresponding to the maximum spin-lattice relax ation rate, is about 10(-9) s. The experimental curves T-1(T, Phi) obtained for the polyisoprene-C7D8, polyisoprene-CCl4 and polyisoprene-CDCl3 soluti ons obey the superposition property. The ESR spectra were recorded from nit roxide labelled molecules (2,2,6,6, tetramethyl piperidin-1-yloxyl) dissolv ed in the polyisoprrne-CCl4 solutions. The analysis of the ESR spectra indi cates only a weak interaction between the nitroxide molecules and the polym eric segments. The correlation time tau(c) of the rotational motion of the nitroxide molecules motion is about 10(-11) s at room temperature. (C) 1999 Elsevier Science B.V. All rights reserved.