UC Santa Barbara

Polymers are commonly used in applications requiring long-term exposure to water and aqueous mixtures including as medical implants, marine antifouling coatings, and water purification membranes. In all of these, the chemistry and structure of the polymer surfaces determine the effectiveness of the final material via interactions with water, dispersed solutes, and larger biomolecular structures. In the past, scientific progress has been made primarily through empirical results derived from chemically distinctive coatings and membranes, but design rules are essential for improving the rate of advancement.

This work leverages a two-pronged approach for relating surface chemistry to its effects on interactions at the water–polymer surface. Design of surfaces containing sequence-defined, peptidomimetic “peptoid” side chains provides fine control over both chemistry and the relative spacing between functional groups, while self-assembled monolayers (SAMs) allow for investigation of model surfaces consisting of a single functional group with negligible surface roughness. This work also includes the development of ambient pressure X-ray photoelectron spectroscopy (APXPS) for studying the chemistry and surface interactions in hydrated polymer surfaces. First, the presence or lack of hydrogen bonding in marine antifouling coatings is found to alter both the polymer’s interactions with water and with soft algal foulers. Afterwards, the capability of side chains to present at the surface and modify polymer hydrophilicity is investigated using APXPS. Finally, the effects of functional group chemistry on the adsorption of small organic molecules are explored in APXPS experiments on model SAM surfaces. The findings of this work indicate that polymer surface chemistry can be modulated by minor changes in composition, and that these changes can have large effects on surface interactions with water, organic molecules, and organisms.