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

Abstract

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

Miscibility in binary blends of poly(vinyl phenol) and poly(n-alkylene 2,6-naphthalates)

“…Horii et al 21 and Mori et al 22 have investigated on the segmental motions of aromatic polyesters containing terephtahloyl and naphthaloyl residues, respectively, using 13 C nuclear magnetic resonance spectroscopy. According to their results, butylene unit is more flexible than the ethylene unit in these aromatic polyesters so that the high chain mobility of PBN may give a faster crystallization rate, 22 and the butylene sequence may be the smallest unit of independent inner motions of the CH 2 sequence in these analogous aromatic polyesters.…”

“…According to their results, butylene unit is more flexible than the ethylene unit in these aromatic polyesters so that the high chain mobility of PBN may give a faster crystallization rate, 22 and the butylene sequence may be the smallest unit of independent inner motions of the CH 2 sequence in these analogous aromatic polyesters. 21 This chemical structure difference should also give rise to the differences in the amount of intermolecular hydrogen bonding interactions when these aromatic polyesters are blended with PVPh. The ester C = O groups of both PEN and PTN can be thought of as dynamically restricted due to the limited mobility for the ethylene and trimethylene units that will not allow the facile orientation of the C = O groups to the PVPh hydroxyl groups.…”

A Brief Review of Poly (Butylene Succinate) (PBS) and Its Main Copolymers: Synthesis, Blends, Composites, Biodegradability, and Applications

“…The crystal structures of PBS have been extensively investigated in the literature using different experimental techniques: X-ray diffraction, electron microscopy, and C NMR [ 63 , 64 , 65 , 66 ]. PBS has two crystalline forms: α and β.…”

Effects of pressure and solvent on the diffusion of aromatic compounds through polymers

“…loc~ is small (the smallest among the three polymers studied) for the following reasons. It is well known that PET is a hydrophobic polymer; its melting point is 270 ~ [29] and the segmental motion of the polymer chain, in the dry state, only initiates around 120 ~ as revealed by Kitamaru and coworkers by the high-resolution 13C NMR (nuclear magnetic resonance) spectroscopy [30]. In the swollen state, as is the case in the present study, however, it is reported [31] that the presence of water shifts Tg of PET to a lower temperature by ca.…”