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2nd Alumni Lecture: Yueh-Lin (Lynn) Loo, Princeton University, “What governs polymorphic accessibility?”


Friday, September 22, 2017 - 1:00pm


163C Campus Center


Reception to follow lecture, on the 10th Floor of the Campus Center (the Amherst Room)


The weak intermolecular forces inherent to molecular crystals give rise to polymorphism, or the ability for these materials to adopt multiple solid-state packing arrangements. Differences in molecular packing can result in distinct materials properties of the same compound (e.g., diamond vs. graphite), making polymorphism of general interest to the materials community. Yet, our collective understanding of this phenomenon remains inadequate. Calculations can shed light on the energetic landscape across different polymorphs but predictions for which phases are preferentially accessed remain challenging because accessibility is often dictated by kinetics (i.e., processing), as opposed to thermodynamics (i.e., energetics). In this talk, I will highlight a framework we have developed that directly correlates the presence short intermolecular contacts with polymorphic accessibility. Subtle changes in the molecular chemistry do not significantly affect the possible solid-state packing arrangements, but do result in differences in the non-covalent intermolecular interactions that ultimately lead to preferential access to specific polymorphs. Case in point is aspirin. Despite Forms I and II being isoenergetic, only Form I is consistently and irreversibly accessed at ambient conditions. This preference stems from the presence of extensive short intermolecular contacts in its crystal structure that precludes any subsequent structural rearrangement. Starting with a series of core-chlorinated naphthalene diimide derivatives, we show this framework to be widely applicable to compounds ranging from molecular semiconductors to pharmaceutics, such as rotinavir, and biological building blocks, such as guanine. In this era of machine learning and materials by design, this framework can facilitate proper selection of functional groups for locking in a prescribed solid-state packing arrangement without adversely affecting desired materials properties.



Yueh-Lin (Lynn) Loo is the Theodora D. ’78 & William H. Walton III ’74 Professor in Engineering and Director of the Andlinger Center for Energy and the Environment at Princeton University.

In the Chemical & Biological Engineering Department, her research focuses on the processing and development of materials for low-cost, lightweight and flexible solar cells and circuits, the combination of which is being explored for a range of applications, including the creation of “smart” windows to increase building and energy efficiencies. More recently, Lynn’s research expanded into economic modeling of liquid fuel production from non-food biomass after her stint at NewWorld Capital Group, a private equity firm that invests in environmental opportunities.

Lynn received her BSE in Chemical Engineering and in Materials Science and Engineering from the University of Pennsylvania in 1996 and her PhD from Princeton University in 2001. She spent a year at Bell Laboratories, Lucent Technologies before joining the faculty in the Chemical Engineering Department at the University of Texas at Austin. She returned to Princeton University in 2007. As the Associate Director of External Partnerships at the Andlinger Center from 2011 to 2015, Lynn launched and led Princeton E-ffiliates Partnership to promote teacher-student-practitioner interactions and foster collaboration with the private sector. She served as Acting Vice Dean of the School of Engineering and Applied Science in the spring of 2016 and was appointed Director of the Andlinger Center in July 2016. With over 100 affiliated faculty members spanning science and engineering disciplines and humanities, the Andlinger Center is developing solutions to ensure our energy and environmental future.

The author of over 140 publications, Lynn has delivered more than 200 invited and plenary lectures globally and she serves on numerous international advisory boards of peer academic institutions, non-governmental organizations, journal publishers and private companies. She is a fellow of the American Physical Society, a Young Global Leader of the World Economic Forum and a Strategic Advisor for NewWorld Capital Group. Her scholarly work has been recognized by numerous accolades, including Sloan and Beckman Fellowships, the John H. Dillon Medal from the American Physical Society, the Peter and Edith O’Donnell Award in Engineering from the Texas Academy of Medicine, Science and Engineering, and the Alan P. Colburn Award from the American Institute of Chemical Engineers.

You can learn more about her and her research group at:, and about the Andlinger Center for Energy and the Environment at


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