Swellable organically modified silica (SOMS) is a new type of material discovered in 2005 by Paul Edmiston and his students in the Wooster Chemistry Department. Like other sol-gel created materials, it absorbs organic chemicals. However, it is dramatically different from similar compounds because it does not absorb water and it can absorb so much organic material that it swells to more than six times its original size. These unusual properties mean that it can be used to clean organic compounds (oil and its byproducts, volatile organic compounds, etc) out of contaminated water. Unlike squishy water-absorbing polymers (often used in disposable diapers or in potting soils), the SOMS exerts a large force during absorption and expansion; the swollen material is still rigid and the absorbed compound cannot be easily squeezed out.
We are interested in the absorption process and resulting expansion of the SOMS material. During the 2010 REU program, Lily Christman began an examination of the material using the atomic force microscope (AFM). She imaged the material in both a swelled and an unswelled state. The force exerted by the material as it swells was also measured at a macroscopic level using a load cell sensor. We plan to continue her preliminary results to investigate the swelling process of the SOMS material by controlling its expansion and measuring the force with which it expands. We have developed an improved version of the load cell device to take more precise measurements of the forces exerted by the material. The SOMS (either powdered or in disk form) is loaded into the cell and a piston is tightened down onto the sample using a finely-threaded screw. By turning the screw, we can control the available volume for the SOMS and thus control its expansion. The cell continuously measures the force exerted by the SOMS during this controlled expansion. By varying the solvent, the chemical preparation of the SOMS, and the physical particle size of the SOMS, we seek to better understand the process of swelling of the material.
The student researcher on this project will devise a systematic and reproducible methodology to make force measurement while allowing the SOMS material to expand. She/he will acquire force data via a computer and LabVIEW software; she/he will analyze the data and ultimately develop a simple physical model to help explain the swelling behavior of the SOMS.