Reports: G5
45840-G5 Experiments for Improved Understanding of the Wetting of Polar Liquids
During the past two years we have made significant progress towards our overarching goals of understanding the wetting of polar liquids on solid surfaces.
The chief personnel outcomes for this grant include the graduation of Kenneth Osborne with a Master of Science degree in August 2009, and the graduation with Bachelor of Science degree of both Kenneth Osborne and Ergys Subashi.
PRF funds, during the first year of the grant were specifically used (1) to purchase supplies and rent gases for our measurements of wetting angles and surface adsorption as a function of pressure,(2) to support one undergraduate student Ergys Subashi, (3) to provide a partial month of summer support for myself, (4) to cover publication costs, and (5) to purchase a Nanoscope reflectometer suitable for quick film thickness determinations.
During the second year, the the equipment and supplies purchased continued to support the research activities of Kenneth Osborne, who graduated with a Bachelor's of Science degree from WPI in May 2008 and continued briefly to complete his Master's degree in my lab, as well as the research of Saonti Chakraborty a graduate student who joined my group in January 2009, focusing on the nature of wetting behavior of polar liquid crystal films on silicon.
As a direct result of the funding provided by our PRF starter grant, we published two research articles the first year, including a Physical Review Letter. During the second year, a follow-up article was submitted to the Journal of Physical Chemistry B, correcting a few inconsistencies in our earlier paper and presenting an improved derivation of the key equation used in our analysis. Ken completed his Master's thesis, which available in electronic form here:
http://www.wpi.edu/Pubs/ETD/Available/etd-062909-113303/
In the thesis, Ken presents the experimental data which is consistent with unexpectedly-large contributions to the contact angle of water droplets due electrostatic double-layer forces. These new results are presently being improved and prepared for journal publications.
As a direct result of successes funded by the PRF grant, we gained substantial additional NSF funding (NSF MRI #0821292) for the purchase of a spectroscopic ellipsometer ($137 000) by which we could significantly expand our wetting and thin film studies to new regimes of temperature and pressure where quartz microbalances and optical observations are not as suitable. Saonti Chakraborty has spearheaded these efforts this year to exploit the new apparatus. Her experiments have significantly extended the phase diagram shown in the Physical Review Letter we published last year, both to much higher thicknesses by by determining the locus of the NA transition in adsorbed liquid crystalline 8CB films in relation to the little understood thin-thick coexistence region. In addition, the experiments reveal a dip in the film thickness which may be related to critical Casimir forces associated with the second order nature of the NA transition. These results are in the process of being improved and prepared for publication later this year.
We also made quartz microbalance measurements of the adsorption of nitrous oxide on gold and are analyzing those results. These results are also presently being prepared for submission to a journal.
