Nuclear magnetic relaxation and the type of distribution of correlation times of segmental motion in rubber

• Published in: Polymer science USSR 1981, Vol.23 (4), p.1042-1054
• Main Authors: Chernov, V.M, Fedotov, V.D
• Format: Article
• Language: English
• ISSN: 0032-3950; 1878-268X
• DOI: 10.1016/0032-3950(81)90495-0

An analysis was carried out of the NMR pulse experiment, which involved the study of the form of reduction of longitudinal and transverse intensity of magnetization and temperature dependence of spin-spin ( T 2) and spin-lattice ( T 1 and T 1 p) relaxation times in rubber (using polyisobutylene (PIB)), in order to explain the form and type of formation of correlation time spectra of segmental motion. It was shown that the correlation time spectrum of molecular motion in polyisobutylene is above T g, which may be satisfactorily described by the superposition of two Fuoss-Kirkwood distribution functions of varying intensity, of which the centres are at a distance of several orders of magnitude. The high-frequency part of the overall spectrum describes small-scale, segmental motion, while the low-frequency part describes large-scale motion related to network fluctuations of linkages. It was established that the existence of this spectrum is determined by special structural features of the macromolecular chain, while the heterogeneity of the sample expressed in structural features of the spin-system, reflects a second order effect-distribution of correlation time spectra.