XPS Studies of Chain Conformation in PEG, PTrMO, and PTMG Linear Polyethers

X-ray photoelectron spectra are reported for ordered and disordered chain conformations of poly(ethylene glycol) and poly(tetramethylene glycol). Both polymers show a conformational dependent intensity change at the top of the (C 2s + O 2s) band of the valence level spectrum, which is interpreted as due to changes in through-space interactions in the corresponding molecular orbitals on going from ordered to disordered chains. We support these conclusions with self-consistent field calculations on model conformations of a poly(ethylene glycol) oligomer. The spectral features at the top of the (C 2s + O 2s) band in the simulated spectra show a strong dependence on rotation about the C−O links of the oligomer chain. The core level spectra of poly(ethylene glycol) and poly(tetramethylene glycol) show no conformational dependence. Angle dependent valence band studies show the presence of a disordered layer at the uppermost surface of a crystalline sample of poly(ethylene glycol). Time dependent valence band studies demonstrate X-ray induced conformational disordering due to chain scission and cross-linking. For poly(trimethylene oxide) core and valence level spectra of only the disordered polymer are reported.