High-resolution 13C spectra and spin-lattice relaxation times Tl have been measured for solid terephthalic acid polyesters [-COC6HlC00(CH2),0-].(m = 2, 3,4, 6, and 10) and succinic acid polyesters , (m = 2 and 4) over a wide range of temperatures above Tp by the 'H scalar-decoupling technique. The high-resolution lines of the individual carbons of the terephthalic acid polyesters appear a t different temperatures, T,, indicating that the carbons differ greatly in molecular mobility. According to the results, they are divided into three groups: terephthaloyl residues, terminal CH2 groups directly attached t o the ester bond, and other central CH, groups in the glycol residues. The molecular mobilities of these groups are strongly dependent on the number m of CH2 groups: for m = 2 and 3, terephthaloyl residues are more mobile than CH, groups, regardless of the existence of two kinds of CH, groups for m = 3. For m 1 4 central CH2 groups become most mobile, whereas terminal CH, groups are still highly restricted in motion.Similar results have been obtained from the measurements of the temperature T-, a t which TI has a minimum value and the segmental motion is described by a shorter correlation time (about 5 X s) than a t T,. On the other hand, all CH2 groups of succinic acid polyesters are almost equally mobile. On the basis of these results the molecular motions of the terephthalic acid polyesters are discussed.
IntroductionMolecular motions of solid polymers have been extensively investigated by measuring dynamic mechanical relaxation, dielectric relaxation, nuclear magnetic relaxation, and other relaxation phenomena. Several relaxation
