Hydrophobicity at the molecular scale: Characterizing the aqueous-polystyrene interface with vibrational sum-frequency generation spectroscopy
Date
2025
Authors
Bevington, Arden
Uddin, Md. Mosfeq
Hore, Dennis K.
Journal Title
Journal ISSN
Volume Title
Publisher
University Of Victoria
Abstract
Interfaces between hydrophobic polymer materials and water are ubiquitous in our everyday lives, from plastic water bottles and raincoats to cutting edge materials and drug delivery capsules. Surprisingly, the molecular-level interactions that occur at their interfaces with water are not well understood. Of particular interest is the origin of the surface charge that has been observed at these interfaces. In this work we investigate water structure and surface charge at the interface with a common hydrophobic polymer, polystyrene, using variable-angle vibrational sum-frequency generation spectroscopy (SFG). SFG is an inherently surface-specific spectroscopic technique that allows us to characterize molecular vibrations at the interface. Variable-angle SFG reveals that water molecules at the surface have a net orientation with their hydrogen atoms pointed towards the surface and show an increase in the magnitude of the surface charge as ionic strength of the solution is increased.
Description
Keywords
physical chemistry, spectroscopy, surface science, charged interfaces