Vibrational and Electronic Excitations in Poly(methylphenylsilane) and Poly(diphenylsiloxane) Films:  Surface Aspects

Abstract

High-resolution electron energy loss spectroscopy (HREELS) is applied to study film surfaces of two silicon-based polymers having methyl and/or phenyl rings as pendant groups: poly(diphenylsiloxane) and poly(methylphenylsilane). These spectra are compared with those obtained by infrared absorption, Raman scattering, and UV/vis absorption spectroscopy for the polymer bulk. Both vibrational and electronic spectra of these two polymers exhibit common features corresponding to the phenyl pendant group excitations. Positions of peaks appearing in HREELS vibrational spectra correspond well to infraredand Raman-active modes of the polymer bulk. Electronic losses also correspond to the electronic excited states of phenyl groups cited in the literature. Differences related to secondary emission and accumulation of relaxed electrons are assigned to the electronic structure of the film. The absence of a loss corresponding to the excitation of polysilane chain is related to a trapping mechanism.

Interaction of Self-Assembled Monolayers of DNA with Electrons: HREELS and XPS Studies

“…However, a good fitting could be obtained yielding Gaussians centered at 3.9, 4.8, 6.0, 7.0, and 7.8 ± 0.2 eV. These values are in good agreement with those found in the electronic HREEL spectra of ultrathin layers containing aromatic groups assigned to a suite of triplet and singlet states . It should be noted here that triplet states can easily be excited by exterior electrons as the spin rule is not broken.…”

“…These values are in good agreement with those found in the electronic HREEL spectra of ultrathin layers containing aromatic groups assigned to a suite of triplet and singlet states. 28 It should be noted here that triplet states can easily be excited by exterior electrons as the spin rule is not broken. Hence, the electronic part of the spectra indicates the excitation of π-π* transitions in the bases through impact electron interactions.…”

Photoprogrammable molecular hybrid materials for write-as-needed optical devices

“…It is clear that there was minimal influence of alkyl chain lengths (length < 4) on the lowest energy absorption peak (associated with the Si-Si trans-planar backbone conformation). Some modification of the absorption intensity, peaking for the methyl-containing compound (PMPS), however, is observed, consistent with prior work on this material [13][14][15]. The di-n-hexyl material (no phenyl moiety) exhibits two distinct absorption peaks (Fig.…”

HREELS Study of Self-Assembled Monolayers of Alkylthiols Functionalized with Oligothiophene Moieties: Extreme Surface Analysis and Evidence for Intermolecular Interactions

“…Furthermore, in short-range interactions, the incident electron can cause distortions of the molecular orbital or suffer electron exchange processes enabling the observation of dipolar forbidden transitions. This has been observed in HREELS spectra of various polymer films such as polystyrene, polyphenylsilanes, and polyphenylsiloxanes, where triplet and singlet states of the benzene pendant groups appear through a sequence of peaks roughly 0.5 eV wide. In this case, where individual electronic excitations of the phenyl groups are detected, we may consider that these chemical groups are dispersed and are not interacting with each other.…”