Department of Chemistry and Biochemistry
Organic/Inorganic/Materials Seminar Series

Professor Pier Alexandre Champagne, New Jersey Institute of Technology
Tuesday March 4, 2025 
3:00 pm in 117 Education 

Hosted by Mike Pluth

Computational and Experimental Approaches to Understand and (Eventually) Control Reactive Sulfur Species

Reactive sulfer species (RSS) are a class of sulfur-based functional groups including H₂S, persulfides (RS₂H), polysulfides (R₂S_n, n>2), nitrosothiols (RSNO), and others, which are now recognized as important biological intermediates with various physiological and pathological effects. This versatile chemistry is due to sulfur’s unique properties, including the stability of all its oxidation states (-2 to +6) and its catenation behavior, leading to a variety of structures with important roles throughout chemistry. Notably, RSS are involved in the H₂S signaling pathways and in the protection of cells against oxidative insult, while polysulfides are also common intermediates in materials science and organic synthesis. Despite the proven importance of RSS and polysulfides, their intrinsic reactivity under organic or biological conditions is still poorly understood due to their thermodynamic and kinetic instability, making experimental characterization, probing, and isolation of individual RSS challenging.

This presentation will showcase our group’s recent efforts in advancing the chemical understanding of RSS, through the application of computational tools (e.g. Density Functional Theory (DFT) calculations) and the development of novel photoactivated small-molecule donors. Various examples of importance for inorganic chemistry, organic synthesis, and chemical biology will be discussed, highlighting the general rules of RSS reactivity that have been uncovered throughout. Overall, our work opens up new possibilities for the study and, eventually, control of polysulfides and RSS in various settings, despite their complicated behavior.

Department of Chemistry and Biochemistry
Physical Chemistry Seminar Series

Professor Achille Giacometti, Ca’ Foscari University, Venice, Italy
March 3, 2024 —2:00pm
Tykeson 140

Phase behaviour and self-assembly properties of semiflexible polymers in solution

This presentation explores the phase behaviour and self-assembly properties of semiflexible polymers in solution, focusing on temperature dependence and bending constraints. The talk is structured in two parts. In the first part, I will examine the phase behaviour of a single semiflexible polymer, comparing two types of bending constraints. The first is the traditional elastic penalty used in the worm-like chain model, while the second is an entropic constraint arising from steric effects introduced by a side sphere. I will demonstrate that these constraints lead to markedly different phase behaviours at low temperatures.

In the second part, I will extend the analysis to multiple polymer chains in solution, investigating their self-assembly properties under each bending constraint. Although the detailed low-temperature behaviour differs between the two constraints, the general self-assembly mechanism appears to exhibit universal characteristics.

Department of Chemistry and Biochemistry
Organic/Inorganic/Materials Seminar Series

Professor Julie Rorrer, University of Washington
Friday, February 28, 2025
3:00 pm, 110 Willamette Hall
Hosted by Teresa Rapp

Advancing the Catalytic Recycling of Polyolefin Waste

Single-use plastics such as polyolefins provide lightweight and effective packaging and materials for food, medicine, and many other consumer products. This has led to massive global generation of plastic waste which is accumulating in landfills and the environment, causing harm to the ecosystem and human health. While a small amount of plastic waste is mechanically recycled, the material quality is diminished compared to virgin polymers. Chemical recycling with heterogeneous catalysis can lower the energy required to selectively break apart polyolefins into higher value fuels, chemicals, and monomers. Emerging methods which can be performed at relatively low temperatures include hydrogenolysis and hydrocracking, solvent-based deconstruction, and tandem hydrogenolysis/aromatization. The scalability of these methods is limited by the high cost of reactants, the requirement for high pressure molecular hydrogen or solvents, and the high cost of catalytic materials. This talk will start by discussing advances in the catalytic depolymerization of waste plastics via hydrogenolysis and hydrocracking, followed by progress in hydrogen-free depolymerization pathways. The talk will close with a discussion on emerging frameworks for the chemical recycling of mixed plastic waste feedstocks and an outlook on remaining technical challenges in polymer upcycling, redesign, and circularity.