Paper Number
PO103
Session
Poster Session
Title
Tribological properties of hard and soft surfaces with grafted polyzwitterionic brushes
Presentation Date and Time
October 17, 2018 (Wednesday) 6:30
Track / Room
Poster Session / Woodway II/III
Authors
- Serfass, Christopher M. (North Carolina State University, Department of Chemical and Biomolecular Engineering)
- Hsiao, Lilian C. (North Carolina State University, Department of Chemical and Biomolecular Engineeirng)
Author and Affiliation Lines
Christopher M. Serfass and Lilian C. Hsiao
Department of Chemical and Biomolecular Engineeirng, North Carolina State University, Raleigh, NC 27606
Speaker / Presenter
Serfass, Christopher M.
Text of Abstract
Recent studies show that biomimetic surfaces with grafted polyzwitterionic brushes can attain extremely low friction coefficients and increased wear resistance. These types of engineered surfaces are increasingly important in applications such as self-cleaning and anti-fouling coatings. Our goal is to investigate the steady state and transient tribological response of hard and soft surfaces as a function of the interfacial dynamics of grafted polyzwitterionic brushes. Here, we employ atom transfer radical polymerization (ATRP) to grow polymer brushes from hard silicon wafers (E ~ 10^11 Pa) and soft poly(dimethyl siloxane) substrates (E ~ 10^6 Pa). This grafting-from process grows monomers one unit at a time from initiators attached a priori onto the surfaces. The polymer brushes are then betainized to produce polyzwitterionic brushes. We characterize polymer brush layers using spectroscopic ellipsometry to determine brush thickness, and Fourier-transform infrared spectroscopy (FTIR) to confirm the presence of appropriate functional groups. Separately, we perform tribological characterization of the native and polymer-grafted surfaces using a ball-on-3-plates geometry attached to a stress-controlled rheometer, in which the surfaces are fully immersed in a liquid medium. We find that betainization changes the friction coefficient of polymer brushes, but fails to produce friction coefficients lower than those of untreated silicon. To address this issue, we will investigate the pre-ATRP chemical modifications and their effects on the surface energy of the substrates.