C-13 NMR INVESTIGATION OF THE LOCAL DYNAMICS OF AN AROMATIC COPOLYESTER IN SOLUTION

The local motions of an aromatic copolyester made from hydroquinone, h ydroxybenzoic acid and isophthalic acid were investigated in trifluoro acetic acid/dichloromethane solution using C-13 n.m.r. The interpretat ion of the C-13 spin-lattice relaxation times was based on results pre viously obtained on arylaliphatic copolyesters obtained from ethylene glycol and hydroxybenzoic acid or isophthalic acid. It was carried out in terms of relatively slow segmental main-chain motions and faster i nternal motions of the aromatic rings. The segmental main-chain motion s were represented by the Dejean-Laupretre-Monnerie orientation autoco rrelation function. In agreement with the poor mobility of the aromati c copolyester, there is not any noticeable libration of the phenyl rin gs. The internal motions of the aromatic rings were described in terms of jumps between two equilibrium positions for the para-substituted p henyl rings and by stochastic jump processes for the isophthalic rings .