Polarized NEXAFS Spectroscopic Studies of Poly(butylene terephthalate), Poly(ethylene terephthalate), and Their Model Compounds

Abstract

Near edge X-ray absorption fine structure (NEXAFS) spectra were obtained using total electron yield detection for poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) and their model compounds 4,4‘-biphenyldicarboxylic acid dimethyl ester (PAM), 4,4‘-biphenyldicarboxylic acid (PCA), and terephthalic acid (TPA). The spectra of PBT and PET were interpreted with the comparison of the spectral features of model molecules and the polarized NEXAFS spectra of oriented films of PAM, PCA, and PBT. From the polarization dependence, the peaks previously ascribed to a C 1s → π*(ring) or π*(ring/CO) excitation at 289.8 eV and an O 1s → 3p/Rydberg or → π*(CO) transition at 536.4 eV were reassigned to a C 1s → σ*(O−CHx) transition and an O 1s → σ*(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 the NEXAFS spectra of polymers.