Date Oct 30, 2024, 12:00 pm – 1:00 pm Location Bowen Hall Auditorium 222 Details Event Description Monitoring Kinetic Processes in Polymers with Low-Frequency Raman SpectroscopyAbstractAmorphous materials universally display low-frequency Raman features related to the phonon density of states resulting in a broad disorder band for Raman shifts below 100 cm-1, which is related to the conformational entropy and the modulus. We have demonstrated that we can measure both glass transition and polymerization kinetics by normalizing the disorder band to its shoulder and monitoring its evolution as a function of time and temperature. We also demonstrate a relationship between the chemical and structural kinetics, which appears to relate to the softness of the material, which we verified via rheological analysis. Low-frequency Raman spectroscopy is, therefore, a promising technique for thermo-structural analysis of polymers. Not only is it chemically agnostic and contactless, but it requires neither intensity calibration nor multivariate analysis. Recently, while using this methodology to study the cure kinetics of an epoxy-amine resin at elevated curing temperatures, we observed repeatable instances of significant anomalous anti-Stokes Raman (AASR) behavior. The spectra returned to normal behavior after the resin vitrified into a glassy state. Through a combination of experimentation and modeling we have been able to provide two complimentary explanations for the observed AASR. By parametrically corelating the intensity of the disorder band (i.e. the change in conformational entropy) with internal energy we can clearly show negative absolute temperature like behavior. Additionally, through statistical physics based non-equilibrium heat flux modeling we demonstrate that a positive heat flow resulting from a phonon population inversion is proportional to the degree of AASR. BiographyRobert V. Chimenti is an Assistant Professor and the Photonics Coordinator with the Department of Physics & Astronomy and the Advanced Materials & Manufacturing Institute (AMMI) at Rowan University. He earned a PhD in Materials Science and Engineering from Rowan University and an MS in Electro-Optics from the University of Dayton. Before transitioning to academia in 2019, Prof. Chimenti had a successful career in the laser and spectroscopy industry, working for companies such as Innovative Photonic Solutions and B&W Tek. During that time, he helped to commercialize many Raman product lines that are still on the market today. Prof. Chimenti’s current research is primarily centered around novel applications of Raman spectroscopy with a particular focus on polymer physics, thermal analysis, and structural kinetics. He is also heavily involved in the development of 3D printing methodologies for polymeric GRIN optics as well as novel SERS and OECT based sensing platforms. Prof. Chimenti spearheaded the launch of Rowan’s Photonics Master’s degree program, and as a community college graduate, is a passionate champion of alternate pathways for non-traditional students. He currently serves as the co-PI for Advancing Photonics Technologies (NSF Engine Development Award #2306326) and serves on the PhotonicsNJ Board of Trustees. Over the past seven years, Prof. Chimenti has also been heavily involved in the organization and management of the SciX conference, having served as the SciX General Chair (21), SciX Workshops Chair (17-20), FACSS Careers Chair (22-23), and Low-Frequency Raman Session Chair (23-present). All seminars are held on Wednesdays from 12:00 -1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.