Next Meeting: The Influence of Molecular Anisotropy on the Structure and Structural Relaxation in Amorphous Solids

2017 Graduate Scholarship Awards

plus keynote address:

The Influence of Molecular Anisotropy on the Structure and Structural Relaxation in Amorphous Solids

Prof. Kenneth R. Morris, Ph.D. (Arnold and Marie Schwartz College of Pharmacy, Long Island University)

The long term stability of amorphous solids formulated as dosage forms is a significant concern due to the inherent instability of the amorphous ‘state’ and the potential for structural changes during storage. Initiation of changes such as those observed on appearance of a more stable crystalline phase, leads to the spontaneous and often catastrophic decrease of critical product performance attributes, including solubility and dissolution rate, which are prerequisite to realizing the bioavailability benefit of amorphous materials used as pharmaceuticals.

One aspect of particular interest to understanding pharmaceutically relevant amorphous solids is the phenomena of structural relaxation. Structural relaxation in this context refers to the physical changes in the locally preferred packing arrangement of molecules or groups of molecules attributed to aging or annealing. It is believed that the packing arrangement of molecules and groups of molecules, including the presence of a secondary (crystalline) phase, influences the physical state and the observed changes in the viscoelastic properties of an amorphous solid during storage. Further, the anisotropy or ‘shape’ of the molecules that comprise these disordered materials plays an integral role in the maintenance of this microstructure.

Effects of molecular anisotropy on the packing patterns and structure relaxation behavior of quench-cooled amorphous solids were investigated using four structurally-diverse model compounds – salicin, indomethacin, felodipine and nifedipine. A simple physical description of each molecule and the description of packing patterns in as-quenched specimens were obtained by methods of direct observation and from total scattering using pair distribution functions. Thermal parameters were acquired by differential scanning calorimetry (DSC). The data suggest that the molecular packing coefficient and the aspect ratios of the molecule, and the common packing distances are related to parameters commonly used to assess structural relaxation by thermal methods.

Date and Location

About the speaker

Dr. Kenneth R. Morris received a dual B.S. in Chemistry and Aquatic Biology from Eastern Michigan University in 1978 and an M.S. in Pharmaceutical Chemistry from the University of Arizona (1986). He received his Ph.D. from the University of Arizona in 1988 and joined E.R. Squibb and Sons. There he developed the Physical Characterization group and co-developed the Materials Science function. He went on to form the Preformulation/Physical Pharmacy group in the Bristol-Myers Products organization, which he led along with Analytical Chemistry. During his time at BMS he also served as a teaching and advising adjunct professor at Rutgers College of Pharmacy and St. Johns University. Dr. Morris moved to the department of Industrial and Physical Pharmacy at Purdue University in the fall of 1997 where he continued his work in Pharmaceutical Materials Science and Industrial Pharmacy where he was a professor and associate head. In 2008 Dr. Morris moved to the University of Hawaii at Hilo to help establish the new College of Pharmacy and Ph.D. program in Pharmaceutical Sciences and was the Department Chair from 2012-2015 and Chair of the Graduate Council for the University. In 2015 Dr. Morris moved to Long Island University as a University Professor and founding Director of the Lachman Institute for Pharmaceutical Analysis. His research and teaching interests include: analytical tools for solid state characterization; the study of the impact of processing on the physical characteristics of formulation components and on subsequent dosage form performance; pharmaceutical unit operation optimization; advanced applications of powder x-ray diffraction and dielectric analysis; the study of the association of water with pharmaceutical solids; and modeling and methods for monitoring processing unit operations. Dr. Morris is an AAPS fellow (American Association of Pharmaceutical Scientists) and was the Purdue University Site leader for the NSF Engineering Research Center for Structured Organic Composites (ERC-SOPS). Professor Morris is a special government employee and past-chair of the U.S. FDA Scientific Advisory Committee for the Office of Pharmaceutical Sciences (ACPS-OPS) advising the agency in his areas of expertise.