Preparation and Separation of C60 Photopolymers for the Physical Chemistry Instructional Laboratory

We report the development of a new physical chemistry laboratory exercise that uses gel permeation chromatography (GPC) to study pristine and photopolymerized C₆₀ materials. GPC is a well-known method for probing molecular weight distributions because of its ability to separate macromolecules based upon size. In this experiment students are interested in the changing molecular weight distribution with irradiation. Students inject both pristine and photoirradiated C₆₀ into the system and analyze the retention time data with a differential UV detector set at 300 nm. The observation of higher molecular weight oligomers upon irradiation is consistent with intermolecular bond formation by the proposed 2 + 2] cycloaddition pathway. The implementation of this laboratory in the classroom has been very successful, generating consistently positive feedback from the students.