ABSTRACT:

Hydrophobic effects play important roles in a wide range of natural phenomena and engineering processes such as coalescence of oil-in-water emulsions, air flotation of mineral particles, folding and assembly of proteins and biomembranes. In this talk, I will review some of our recent experimental advances in characterizing the hydrophobic interactions by direct force measurements at polymer/water and deformable air/water and oil/water interfaces. Results will be shown on the effects of dissolved gas, specific ions, and spontaneous cavitation of confined water film between approaching hydrophobic polymer surfaces in degassed solution. Synchronous measurements of interaction forces of deformable bubbles/drops with sub-nN resolution and drainage dynamics of confined thin liquid films down to nm thickness were achieved for the first time. We have also quantified the nanomechanics between water or oil drops and various polyelectrolyte surfaces (i.e., zwitterionic, cationic and anionic), and elucidated the intrinsic wetting mechanisms of the polyelectrolyte surfaces in oil/water media. An intriguing long-range “hydrophilic” attraction was found between water drops and polyelectrolyte surfaces in oil, with the strongest interaction measured for the polyzwitterion. These results provide useful insights into the development of novel polymer-based functional materials and coatings for a wide range of engineering, bioengineering and environmental applications.

BIO:

Hongbo Zeng is a Professor in the Department of Chemical and Materials Engineering at the University of Alberta, and holds a Canada Research Chair (Tier 1) in Intermolecular Forces and Interfacial Science. He received his Bachelor of Science and Master of Science degrees at Tsinghua University in 2001 and 2003, respectively, and obtained his PhD at the University of California, Santa Barbara in 2007 under the supervision of Prof. Jacob Israelachvili and Prof. Matthew Tirrell. Zeng’s research interests are in colloid and interface science, functional materials & nanotechnology, with a special focus on intermolecular and surface interactions in soft matter (e.g., polymers, biopolymers, surfactants, emulsions) and engineering processes, and development of functional materials. Zeng has published over 160 refereed research journal articles and 7 book chapters, edited a book “Polymer Adhesion, Friction and Lubrication” (Wiley), and holds 9 patents (6 granted and 3 pending). Zeng received the Peebles Award of the Adhesion Society (2007), Materials Research Society (MRS) Graduate Research Award (Silver Medal) (2007), Petro-Canada Young Innovator Award (2013), Martha Cook Piper Research Prize (2016), and The Canadian Journal of Chemical Engineering Lectureship Award (2016).