Optical Properties and van der Waals - London Dispersion Interactions of Polystyrene Determined by Vacuum Ultraviolet Spectroscopy and Spectroscopic Ellipsometry

Abstract

The interband optical properties of polystyrene in the vacuum ultraviolet (VUV) region have been investigated using combined spectroscopic ellipsometry and VUV spectroscopy. Over the range 1.5-32 eV, the optical properties exhibit electronic transitions we assign to three groupings, E 1 , E 2 , and E 3 , corresponding to a hierarchy of interband transitions of aromatic (π → π*), non-bonding (n → π*, n → σ*), and saturated (σ → σ*) orbitals. In polystyrene there are strong features in the interband transitions arising from the side-chain π bonding of the aromatic ring consisting of a shoulder at 5.8 eV (E 1 ) and a peak at 6.3 eV (E 1 ), and from the σ bonding of the C-C backbone at 12 eV (E 3 ) and 17.1 eV (E 3 ). These E 3 transitions have characteristic critical point line shapes associated with one-dimensionally delocalized electron states in the polymer backbone. A small shoulder at 9.9 eV (E 2 ) is associated with excitations possibly from residual monomer or impurities. Knowledge of the valence electronic excitations of a material provides the necessary optical properties to calculate the van der Waals-London dispersion interactions using Lifshitz quantum electrodynamics theory and full spectral optical properties. Hamaker constants and the van der Waals-London dispersion component of the surface free energy for polystyrene were determined. These Lifshitz results were compared to the total surface free energy of polystyrene, polarity, and dispersive component of the surface free energy as determined from contact angle measurements with two liquids, and with literature values. The Lifshitz approach, using full spectral Hamaker constants, is a more direct determination of the van der Waals-London dispersion component of the surface free energy of polystyrene than other methods.

Broadband measurements of aerosol extinction in the ultraviolet spectral region

“…These values are lower than the retrieved values reported here. However, the values reported here are more consistent with Chartier and Greenslade (2012), who recently measured a real part of the refractive index n = 1.81 (±0.03) at λ = 248 nm and n = 1.72 (±0.02) at λ = 335 nm, which is greater than the results reported for particles in suspension by French et al (2007) and Ma et al (2003).…”

“…Refractive indices have been reported for bulk samples (Matheson and Saunderson, 1952;Nikolov and Ivanov, 2000;Sultanova et al, 2003), particles in suspension (Bateman et al, 1959;Smart and Willis, 1967;Ma et al, 2003;French et al, 2007), and aerosol particles (Pettersson et al, 2004;Abo Riziq et al, 2007;Baynard et al, 2007;Lang-Yona et al, 2009;Chartier and Greenslade, 2012). These measurements are nicely summarized by Miles et al (2010), with the exception of the more recent Chartier and Greenslade (2012) result.…”

Adhesive interactions of geckos with wet and dry fluoropolymer substrates

“…Hamaker coefficients, A TWA 121 , were calculated using literature values for the indices of refraction (table 1). The interfacial energy between two dissimilar materials was calculated using the index of refraction of one material for the isotropic blocks, and the index of refraction of the second for the medium [29,42].…”

New perspectives on van der Waals–London interactions of materials. From planar interfaces to carbon nanotubes

“…For the optically isotropic-planar case we use full spectral optical properties of alumina [16] and polystyrene [17] across water. The water spectra is developed from the index of refraction oscillator model detailed in Parsegian [6].…”