Change in Structure of Poly(ethylene-1,2-diphenoxyethane-p,p'-dicarboxylate) by Annealing

The structure change on annealing of poly(ethylene-1,2-diphenoxyethane-p,p'-dicarboxylate) (PEBC) was studied by high-resolution solid-state ¹³C NMR spectroscopy. The ¹³C CP/MAS spectra of the annealed samples showed a doublet for the aromatic carbons at 3- and 5-positions, which gave a single peak for the quenched sample, as shown in Fig. 1.

Fig. 1. ¹³C CP/MAS NMR spectra of annealed and quenched samples. The vertical bars under the spectra indicate the peak positions observed in solution. The marks ^* indicate spinning sidebands.

No other carbons showed any evidence of splitting. This indicates that the splitting arises not from polymorphic forms but from the effect like the gamma shielding effect. The noncrystalline component of the samples annealed at a temperature higher than 100�� exhibited the same NMR line shape as that of the sample annealed at 70�� instead of the quenched sample. Since the T_1C decay curves showed a non-single exponential decay, the spectrum was decomposed into several spectra, each of which corresponded to a different T_1C value. It is suggested that the distribution of molecular mobility in the noncrystalline region of the annealed sample changes with the annealing condition.