CHAIN MOBILITY OF SOME TEREPHTHALIC ACID POLYESTERS IN SOLUTION - C-13 SPIN-RELAXATION STUDY

In the reported experiments, carbon-13 spin-lattice relaxation times (T//1), nuclear Overhauser enhancements (NOE), and resonance linewidths ( DELTA nu ) 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 chi **2 distribution 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.