Surface Orientation of Phenyl Groups in Poly(sodium 4-styrenesulfonate) and in Poly(sodium 4-styrenesulfonate):Poly(3,4-ethylenedioxythiophene) Mixture Examined by Sum Frequency Generation Vibrational Spectroscopy

Abstract

Sum frequency generation (SFG) vibrational spectroscopy was used to investigate the surface phenyl ring orientations of spin-coated poly(sodium 4-styrenesulfonate) (PSSNa) and of PSSNa in the spin-coated polymer material Baytron P. Baytron P is a commercially available conducting polymer suspension with poly(3,4-ethylenedioxythiophene) (PEDOT) and PSSNa in water, which is widely used in organic electronic devices. SFG spectra collected using different polarization combinations showed that the twist angles for the phenyl groups on the spin-coated PSSNa and Baytron P surfaces were not random; therefore, both the twist and tilt angles needed to be deduced in order to determine their respective phenyl group orientations. Results indicated that on the PSSNa surface, the para-substituted phenyl ring has a tilt angle of 47.5 degrees +/- 5.3 degrees and a twist angle of 58.8 degrees +/- 8.2 degrees. The tilt and twist angles, 48.2 degrees +/- 3.6 degrees and 65.2 degrees +/- 4.0 degrees, respectively, were determined for the Baytron P phenyl ring, which were not very different from those of PSSNa phenyl groups on the surface.