Chain mobility of some terephthalic acid polyesters in solution. A ¹³C spin‐relaxation study

Abstract

Carbon‐13 spin‐lattice relaxation times (T1), nuclear Overhauser enhancements (NOE), and resonance linewidths (Δp) have been measured for a series of terephthalic acid polyesters containing ethyl, butyl, hexyl, and isopropyl groups between neighboring terephthalate units. The relaxation parameters of all carbons in the terephthalate groups are independent of the length of the separating alkyl chain. Reduced NOE's are seen for all carbons. The data are interpreted in terms of a log X2distribution of correlation times of constant width, but variable average mobility. The average mobility in the alkyl chain increases with increasing distance from the terephthalate group in a given polymer. For a given position in the chain. mobility increases with increasing chain length. This behavior is consistent with the presence of independently reorienting, highly solvated terephthalate groups.

Dynamics of macromolecular chains in solution. Nuclear magnetic relaxation of aryl-aliphatic polyesters

“…The nuclear Overhauser enhancement measured on these nuclei at 25 MHz is maximum over the range of temperature of interest. As well as the 27 °C data, these variable-temperature data are well represented by the isotropic r0 process, the values of which are given in Figure 2, and internal phenyl ring reorientation rir. The activation energies for the latter motion are summarized in Table III.…”

Long-range segmental motion in polymers: a carbon-13 nuclear magnetic resonance spin-lattice relaxation study of polyesters

“…Komoroski did, in fact, find values much shorter than those we have observed for a number of polyesters dissolved in hexafluoroisopropyl alcohol. 33 This is a solvent which should hydrogen bond strongly to the ester groups. The fact that he worked at lower magnetic field strengths, however, makes uncertain whether the shorter relaxation times were a solvent or a field effect.…”

Molecular mobilities of individual constituent carbons of solid polyesters above Tg as studied by carbon-13 nuclear magnetic resonance spectroscopy

“…broad-line first-derivative NMR spectra were also obtained for the same samples used in the 13C NMR measurements with a JNM-PW-60 NMR spectrometer (JEOL) at a frequency of 60 MHz. The magnetic field was modulated at 35 Hz and an amplitude of 0.05-0.08 mT.…”