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Directly Probing Molecular Ordering at the Buried Polymer/Metal Interface 2: Using P‑Polarized Input Beams

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journal contribution
posted on 14.08.2012, 00:00 by Xiaolin Lu, Gi Xue, Xinping Wang, Jianglong Han, Xiaofeng Han, Jeanne Hankett, Dawei Li, Zhan Chen
Previously, we developed several methods to use sum frequency generation (SFG) vibrational spectroscopy to probe buried polymer/metal interfaces in situ by depositing polymer films with different thicknesses on metal surfaces or sandwiching a polymer thin film between a metal surface and a fused silica window. In this study, we developed a new and easier method to directly probe the polymer/metal interface by collecting ppp SFG spectra using a poly­(ethyl methacrylate) (PEMA)/silver (Ag) interface as an example. We confirmed that for a thin polymer film on metal, the dominant SFG signals were contributed from the polymer surface in air and/or the polymer metal interface, while the contribution from the polymer bulk could be ignored. Previously, we showed that the ssp spectra were contributed by both the polymer/air and polymer/metal interfaces. Here we demonstrated that the SFG ppp spectra were dominated by signals from the buried polymer/metal interface from which the structural information on the buried interface can be deduced. This method to probe the buried polymer/metal interface via SFG is relatively simple compared to our previous sample preparation techniques and/or data analysis methods.