Friday August 3, 2007

Lots of work today. By 9AM we had set up the 0.08% surfactant solution in the Hasbrouck lab and returned to Conte. Each of us again spin coated 3 films of 1.4% polystyrene in toluene, then returned to Hasbrouck to float and wrinkle. The more surfactant present, the greater the difficulty floating the films, but the easier it is to manipulate the films into position under the microscope. I had success with two films, Dave was able to complete the wrinkling protocol for one film, and Efren's films just would not let go of the glass slide. We decided that it was necessary to increase the angle of the slide as it entered the water, and I found that I had to use the probe to move the liberated film away from the glass surface so that it would not re-adhere before I could remove the slide from the water.

A noon lunch of pizza was followed by a presentation by Chelsea, who is a first year PhD candidate from N.C. State. She has a BS in Textile Engineering and has worked in industry for several years since her graduation. She is affiliated with the Crosby Group and is working on the interactions that occur at the interfaces of soft matter. She took a few minutes to explain a little more about the PhD program; there are 30 hrs of coursework during the first year, including classes in Polymer Synthesis Chemistry, Materials Engineering, Polymer Physics, Synthetic Chemistry and Polymer Characterization. This is a heavy load for first year students. In addition to the coursework, they are beginning research and working to decide which area of polymers they will focus on for their PhD (this also includes selecting one of the professors to serve as research supervisor).

After Chelsea's presentation, we attended the Crosby group meeting to see Renee, Mary and Lauren present the results of their research. Their experience here has been quite different from ours. They have made several discoveries which Dr. Crosby believes to be worthy of publication. Their research project is entitled "Long Range Alignment of Surface Wrinkling".

During their experiments, they have used PDMS (polydimethylseloxane) films about 1mm thick, which they have then subjected to horizontal stress. After stressing, the PDMS is soaked in ethanol to induce swelling. Cracks form in the PDMS perpendicular to the strain plane, while wrinkles occur after ethanol exposure that are parallel to the strain plane. The wavelength and amplitude of the wrinkles are related to the length of time the PDMS is stressed.

Lauren, who is an art teacher, demonstrated the media she has artistically "stressed" to reproduce wrinkling in her classroom. Her greatest success was achieved with tissue paper, clear acrylic medium, and foamboard. She was able to form and maintain wrinkles of the same wavelength when the tissue paper was applied over the acrylic medium to the foamboard. It was really neat to see the applications for the art classroom.