05/17/2021
By Matthew Gage
The Kennedy College of Science, Department of Chemistry, invites you to attend a proposal defense by Sevil Kaynar Turkoglu entitled “Extreme wetting surfaces: the effect of surface topography and composition.” The defense will be held on May 28, 2021 at 11 a.m. on Zoom. Please contact Matthew Gage for meeting information if you are interested in attending.
The committee will be composed of Joey Mead (committee chair), Hanna Dodiuk, Shmuel Kenig, Jinde Zhang, Jo Ann Ratto Ross, James Whitten and Marina Ruths. A brief abstract is provided below.
All interested students and faculty members are invited to attend.
Abstract: The surface wetting, the process of water interacting with a surface, is an essential factor in many practical applications. In this work, two extreme cases of wetting: superhydrophilicity and superhydrophobicity is studied.
In the chapter 1, the effect of particle loading on the wetting properties of coatings was investigated by modifying a coating formulation based on hydrophilic silica nanoparticles (22nm) and poly (acrylic acid) (PAA). Water contact angle (WCA) measurements were conducted for all coatings to characterize the surface wetting properties. Wettability was improved with an increase in particle loading. The resulting coatings showed superhydrophilic (SH) behavior when the particle loading was above 53 vol. %. No new peaks were detected by attenuated total reflection (ATR-FTIR). The surface topography of the coatings was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The presence of hydrophilic functional groups and nano-scale roughness were found to be responsible for superhydrophilic behavior. The surface chemistry was found to be a primary factor determining the wetting properties of the coatings. Adhesion of the coatings to the substrate was tested by tape test and found to be durable. The antifogging properties of the coatings were evaluated by exposing the films under different environmental conditions. The superhydrophilic coatings showed anti-fogging behavior. The transparency of the coatings was significantly improved with the increase in particle loading. The coatings showed good transparency (>85% transmission) when the particle loading was above 84 vol. %. Finally, the spreading dynamics of water droplets on of the coatings was investigated by following the droplet diameter with respect to time. It was found that the spreading velocity expanded with an increased roughness factor.
In the chapter 2, two different strategies were developed to improve the transparency of superhydrophilic coatings. First strategy was conducted by using the smaller size (7nm) hydrophilic silica particles along with the polyacrylic acid in the nanocomposite formulation. The transparency of the coatings was significantly improved with the decrease in particle size. The increase in particle loading decreased the water contact angle which is the indication of improving surface hydrophilicity. Superhydrophilic behavior was achieved when the particle loading was 30 vol.% and above. The second strategy involves the use of neat ionomer instead of nanocomposite formulation. The prepared coatings showed good transparency (>90% transmittance) on different substrates. The effect of the molecular weigh on the antifogging performance was also studied. The coatings having molecular weight 225000 were resulted in better antifogging property.
Chapter 3 presents the work that aims to develop environmentally friendly superhydrophobic coatings using non-hazardous solvents and non Polyfluorinated Alkyl Substances (PFAS) materials. The formulation will be developed with the hydrophobic silica, epoxy and non-fluorinated hydrophobic silane components. The formulated coatings will be coated on various substrates by spray coating method. Anti-icing, anti-corrosion and drag reduction performances of the coatings will be evaluated.