Absolute Characterization of Crosslink Density
Student Researchers: Alexandra Kuzmishin and Adam Trontz
Faculty Advisors: Sarah Schmidtke (Chemistry)
The experimental chemistry team worked this summer to develop a method to directly measure the crosslink density of rubber samples. The strategy was to adapt a common biochemical technique to measure disulfide bonds, the chemical bonds that link polymer units in the rubber, through a reaction with Ellman's reagent. This reagent produces a chromophore upon reaction with disulfide bonds, which can be visualized using UV-VIS spectroscopy to quantify the number of disulfide bonds that reacted. A key difficulty in this adaptation is the organic nature of rubber, relative to the aqueous matrix necessary for the Ellman's reaction. Some of the milestones accomplished in this project were: determination of co-solvent buffer system allowing for the Ellman's reagent reaction and solubilizing the rubber, obtaining a linear calibration curve for the cysteine standard in the co-solvent system, development of a purification and reduction method for the rubber sample, qualitative proof of principle that the technique works for solid rubber samples, and preliminary quantitative data yielding concentration of disulfides within the anticipated order of magnitude for tire rubber.