CAREER: Solid-State and Materials Chemistry applicable to Titanean Model Planetary Ices

Southern Methodist University, Dallas TX

Investigators

Abstract

PART 1: NON-TECHNICAL SUMMARY With this NSF CAREER award, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, the principal investigator and his research group carry out experimental research on the crystallization and solid phases of some of the smallest organic molecules. Such chemicals, like benzene and acetonitrile, are frequently used as liquid solvents and/or fuels in industry and everyday life, but they are also produced in the atmosphere of Titan, Saturn’s icy moon. Carried by rainfall, they descend on the surface of Titan, where they crystalize as planetary ices. Surprisingly, there are many open questions about the solid-state and materials chemistry of these smallest organic compounds which are relevant as materials on Earth, and minerals on Titan. This NSF CAREER project includes detailed experimental characterization of the solid-state structure and the composition of these materials systems that consist of two or more individual molecular components that crystallize as one material with new properties. Of particular interest, in this regard, is the discovery and design of novel low-temperature thermal expansion materials (solids for which the physical size drastically changes upon heating and cooling), and of materials that can be used for the synthesis of other functional solid-state materials. The studies on the self-assembly of small and prebiotic molecules into organic minerals and (planetary) ices, are also relevant to two of the NSF’s 10 Big Ideas: Windows on the Universe, and Understanding the Rules of Life; and with the design of low-temperature functional materials, the research connects to another of the 10 Big Ideas: Navigating the New Arctic. Along with the experimental research, this NSF CAREER award educates a new generation of materials scientists and equips them with the knowledge and skillset to address challenging and long-standing questions in materials characterization. High-school students become engaged in STEM activities, and possibly motivated to pursue STEM careers, with the help of journal cover art and table of graphical content design. PART 2: TECHNICAL SUMMARY This NSF CAREER award, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, focuses on elucidating the structure and composition of fundamentally relevant multicomponent organic systems, comprised of the smallest organic molecules, such as benzene, pyridine, acetonitrile, propionitrile, butanenitrile, etc.. This research is in part motivated by the recently concluded Cassini-Huygens mission, which revealed that the surface of Saturn’s moon Titan harbors large inventories of small organic molecules, solidified and crystalized as planetary ices. The project addresses major gaps in the structural and compositional knowledge and understanding of the smallest organic systems. Most notably, the binary and ternary phase diagrams of these systems are vastly underexplored, and the crystal structures of some of them remain unknown, centuries after their discovery. This research establishes the phase equilibria in these multicomponent systems, and provides a detailed structural account on the crystal, local and dynamic structure of their solid-state by employing X-ray and neutron diffraction and spectroscopy, Raman, infrared and neutron spectroscopy, and calorimetric techniques. The obtained knowledge on the structure and composition of these systems opens a plethora of possibilities for the design and development of new functional materials, for example colossal thermal expansion properties. This expansivity can be leveraged in the design of modular thermal expansion materials for low-temperature applications. The unique arrangement of these molecules in the crystal lattice also allows for unprecedented solid-state reactivity and synthesis of multicomponent extended solids with modified or functionalized graphene- or diamond-like structures. These extended solid materials have myriad of potential applications at ambient conditions. The educational segment of this NSF CAREER award contributes to training of the new generation of materials researchers, equipped with the knowledge to solve crystal structures from powder diffraction data. Additionally, the principal investigator engages high-school students with the help of cover art and table of graphical content design. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.