Investigation of sub-monolayer, monolayer, and multilayer self-assembled semifluorinated alkylsilane films.

Semifluorinated self-assembled (FAS SA) films fabricated from trifunctional precursors are frequently used in myriad applications, yet an understanding of the effects of fabrication conditions, including deposition time, on adsorption mechanisms and molecular architectures is still being developed. In this work we prepared SA films based on the F(CF(2))(8)(CH(2))(2)SiCl(3) (FAS-17) precursor and characterized these films using a suite of surface analytical techniques. Contact angle, sum frequency generation (SFG) spectroscopy, X-ray photoelectron spectroscopy (XPS), and ellipsometry results are consistent with the formation of disordered sub-monolayer structures at short deposition times, well-ordered monolayers at intermediate deposition times, and inhomogeneous multilayers at long deposition times.

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.

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.

Surface structures of an amphiphilic tri-block copolymer in air and in water probed using sum frequency generation vibrational spectroscopy.

Sum frequency generation (SFG) vibrational spectroscopy has been applied to investigate surface structures of an amphiphilic surface-active block copolymer (SABC) film deposited on a CaF(2) substrate, in air and in water in situ. Developed as a surface-active component of an antifouling coating for marine applications, this amphiphilic triblock copolymer contains both hydrophobic fluorinated alkyl groups as well as hydrophilic ethoxy groups. It was found that surface structures of the copolymer film in air and in water cannot be probed directly using the SFG experimental geometry we adopted because SFG signals can be contributed from the polymer/air (or polymer/water) interface as well as the buried polymer/CaF(2) substrate interface.

Real-time structural investigation of a lipid bilayer during its interaction with melittin using sum frequency generation vibrational spectroscopy.

Interactions between membrane bilayers and peptides/proteins are ubiquitous throughout a cell. To determine the structure of membrane bilayers and the associated peptides/proteins, model systems such as supported lipid bilayers are often used. It has been difficult to directly investigate the interactions between a single membrane bilayer and peptides/proteins without exogenous labeling.