Introduction of Modern Light Scattering Methods in Chemistry Laboratories

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This proposal seeks to introduce modem light scattering instrumentation into our chemistry laboratories, especially our physical chemistry and biochemistry laboratories. The characterization of macromolecules, whether they be synthetic polymers or biological, depends heavily on the measurement of molecular weight and size. Light scattering techniques have long been recognized as one of the best means of determining molecular weight and size. Advances in instrumentation, largely made possible by the laser and improved photometric detection devices, have now made such techniques accessible for use in undergraduate laboratories. As examples, two of the several experiments proposed here will allow physical chemistry students to explore properties of diblock copolymers and micellar solutions of surfactants: (1) the transition from a random coil conformation to a globule conformation will be studied for a diblock copolymer system; (2) the size and polydispersity of self-assembled aggregates in aqueous surfactant systems will be studied. Biochemistry students will test the validity of get permeation calibration curve methods for molecular weight measurements against absolute molecular weight measurements made by light scattering methods. All the planned experiments are made extremely facile by the requested instrumentation whose data acquisition time represents such a saving in laboratory time that students will be able to explore further aspects of the projects on their own thereby enriching their laboratory experiences within the same currently available time frame. The advent of the new instrumentation can only encourage students to appreciate more fully the challenges available in the extremely important, increasingly interdisciplinary field of macromolecular science.