POLARIZED NEXAFS SPECTROSCOPIC STUDIES OF POLY(BUTYLENE TEREPHTHALATE), POLY(ETHYLENE-TEREPHTHALATE), AND THEIR MODEL COMPOUNDS

Near edge X-ray absorption fine structure (NEXAFS) spectra were obtain ed using total electron yield detection for poly(butylene terephthalat e) (PBT) and poly(ethylene terephthalate) (PET) and their model compou nds 4,4'-biphenyldicarboxylic acid dimethyl ester (PAM), 4,4'-biphenyl dicarboxylic acid (PCA), and terephthalic acid (TPA). The spectra of P ET and PET were interpreted with the comparison of the spectral featur es of model molecules and the polarized NEXAFS spectra of oriented fil ms of PAM, PCA, and PET. From the polarization dependence, the peaks p reviously ascribed to a C 1s --> pi(ring) or pi*(ring/C=O) excitation at 289.8 eV and an O 1s --> 3p/Rydberg or --> pi(C=O) transition at 536.4 eV were reassigned to a C 1s --> sigma(O-CHx) transition and an O 1s --> sigma(O-CHx) transition, respectively. The present results demonstrate that the polarization dependence of the NEXAFS spectra of oriented small analogous molecules are useful for the assignment of th e NEXAFS spectra of polymers.