Often, in scientific or technological areas governed by physicochemical principles-areas such as, adhesion, coatings, catalysis, cell biology, and biomedical implants-there are problems that involve the coming together of two immiscible substances. The boundary region at which the phases of such substances meet is defined as the interface. Observable interfacial phenomena are dictated by the nature and organization of molecules originating from each of the two phases and residing in the interface. In most instances, the latter is inferred from the former-for example, wettability studies and friction measurement may suggest the preference of certain types of molecules, and perhaps even their structure, at the interface. Knowledge of the underlying, molecular origins is important because the composition and architecture of molecules can be controlled by chemical synthesis; therefore, proven molecular mechanisms for interfacial phenomena are of great value in controlling the behavior of two substances at their mutual interface. However, because several buried or hidden interfaces (e.g., solid-solid and solid-liquid) are inaccessible, in situ, by conventional surface-science techniques that require vacuum, traditionally researchers have resorted to indirect and ex situ routes to obtain the molecular-level picture. In the last decade, we have used SFG to study polymer-air, polymer-liquid, polymer-polymer, and polymer-solid interfaces.
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Anim-Danso, E.; Zhang, Y.; Dhinojwala, A. “Freezing and Melting of Salt Hydrates Next to Solid Surfaces Probed by Infrared−Visible Sum Frequency Generation Spectroscopy” J. Am. Chem. Soc 2013, 135, 8496-8499.
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Alizadeh, A.; Yamada, M.; Li, R.; Shang, W.; Otta, S.; Zhong, S.; Ge, L.; Dhinojwala, A.; Conway, K. R.; Bahadur, V.; Vinciquerra, A. J.; Stephen, B.; Blohm, M. L. “Dynamics of Ice Nucleation on Water Repellent Surfaces” Langmuir 2012, 28(6), 3180-3186.
Li, G.; Dhinojwala, A.; Yeganeh, M. S. “Interference Effect from Buried Interfaces Investigated by Angular-Dependent Infrared-Visible Sum Frequency Generation Technique” J. Phys. Chem. C 2011, 115(15), 7554-7561.