NMR-Untersuchungen über molekulare Bewegungsprozesse in Phenylensulfiden

Abstract

NMR Studies of Molecular Motions in Phenylene SulfidesInternal motion in poly (p-phenylene sulfides) and in some low-molecular phenylene sulfides has been studied using NMR relaxation and broad line techniques. The relaxation rates T\~l in the laboratory frame at 30 or 15 MHz, and T^1 in the rotating frame at 45 kHz, and the second moments (or local fields or linewidths) have been measured over an extended range of temperatures for five different materials. For the polymers, the most important process has an activation energy of approximately 40 kJ/mole; it is ascribed to reorientational random oscillations of the phenylene groups, and it depends upon the detailed polymer structure. The origin of further processes of motion observed with activation energies of 20 and 11 kcal/mole is discussed. The rather narrow lines which occur in the NMR spectra at temperatures well above the glass transition are explained by the mobile fraction of chains of the non-crystalline regions.

High Temperature Study of Molecular Motion in Polyphenylene Sulfide by Thermally Stimulated Currents

“…This peak is independent of the choice of electrodes, the temperatures of the current maximum Fm depends on the temperature of polar ization (this peak was present only in samples polarized at temperatures close to Fg and higher) and the peak is most pronounced for samples polar ized at 150 °C and at higher temperatures. We relate this peak to the same process as that observed in NMR experiments at 150 °C [3], namely the appearance of reorientational motions of the chains or their segments.…”

“…Well resolved TSC peaks were obtained, and we calculated the activation energy and the respective total charge for these thermograms [5]. We were moreover able to identify a TSC peak at about 150 °C, which appears to be related with the same process as the decrease in second moment in NMR experiments observed at 150 °C [3]. This we attrib uted to reorientation of PPS chains.…”

“…The degree of crystallinity, determined by Brady [12] by X-ray diffraction is 65%, whereas Chen Ji Zhou found 75% [13,14]. The same degree of crystallinity was esti mated by Jurga et al applying the NMR method [3], The crystalline melting point lies at about 295 °C [11].…”

“…The elastic properties of PPS have been studied by Eisenberg and Cayrol [1] and the dielectric relax ation by Rigby and Dew-Hughes [2], Various relax ation mechanisms have been proposed in various temperature regions and have been attributed to the rotational and torsional motion of the phenylene groups. More information on the molecular dynam ics has been gained from the NMR investigation of Jurga et al [3], who suggested to relate the relax ation process in the low temperature region with the conformational motion of the phenylene rings be tween two equipotential equilibrium states with an activational barrier of the order of 10 kJ/mol (0.1 eV). At high temperatures the reorientational motion of the phenylene groups seems to play a more important role.…”

Molecular dynamics of poly(ethylene terephthalate)/poly(phenylene sulfide) nanocomposites with barium titanate

“…It was assumed that the phenyl ring jumps between two unequal states have the most influence on the spin-lattice relaxation rate below the glass transition temperature [18,19]. The contribution of phenyl flip motion to spin-lattice relaxation rate can be described by [20,21] …”