Wednesday, September 17, 2014, 11:00 AM
Dr. Robert Q. Topper (Cooper Union)
Computational Studies of Nanoparticles
The reaction between ammonia and hydrogen chloride to form solid NH4Cl has been studied for many years, serving as a prototype system for an improved understanding of acid-base chemistry. Recently, studies have found that aerosols containing NH4Cl particles form atmospherically in polluted marine and coastal environments. This motivated us to try to predict the relative stabilities of differently-sized NH4Cl nanoparticles in the gas phase. In this lecture we will discuss our methods and findings, as well as our current work on other ammonium halides.
Thursday, October 2, 2014, 6:00 PM (The LI-ACS Seminar)
Dr. Robert B. Grubbs (Stony Brook University)
From Molecules to Macromolecules to Materials: Controlling Structure through Synthesis
The control over structure facilitated by modern synthetic techniques enables control over the assembly of molecules and macromolecules in functional materials. We have designed and synthesized several classes of block and star-block copolymers with stimulus-responsive components. These polymers form assemblies with shapes and sizes that are dependent upon specific conditions. For example, we have investigated a range of synthetic systems that are designed to assemble in water into smaller micellar aggregates at low temperatures and larger vesicles at higher temperatures. The structural shifts in these systems under specific conditions will be discussed. A number of factors, including block size and extent of interblock interactions, appear to be important in controlling transformation rate. We will describe the design of these and other systems and our efforts to better understand the behavior of the resulting materials.
Thursday, November 6, 2014, 6:00 PM (The LI-ACS Seminar)
Dr. Daniele Musumeci (York College, CUNY)
Surface Crystal Growth and Stabilization of Amorphous Pharmaceutical Solids
Glasses are amorphous materials that combine the mechanical stability of solids with the microscopic spatial uniformity of liquids, making them ideal for many applications, including electronics, bio-preservation and drug delivery. Amorphous solids, however, are inherently unstable, and can crystallize over time, sometimes surprisingly fast. Recent studies have discovered that as organic liquids are cooled to become glasses, crystal growth at the free surface can be substantially faster than in the interior. This phenomenon is uncommon for inorganic materials and it is generally terminated as the glasses are heated to become liquids. We have applied scanning electron microscopy (SEM) and real-time atomic force microscopy (AFM) to investigate the surface crystal growth on glassy indomethacin (IMC), an anti-inflammatory drug, in the alpha and gamma polymorphs. The high-resolution microscopies provided complete micro-structural details of surface crystal growth. We observed that surface crystals rise hundreds of nano-meters above the amorphous surface as they grow laterally, and are surrounded by depletion zones. Upon heating above the glass transition temperature, the onset of liquid flow embeds upward-growing surface crystals and terminates their growth, but this effect is remarkably mild for the gamma polymorph of IMC. This effect arises because the velocity of liquid flow exceeds the growth front velocity, causing the wetting and embedding of upward-growing surface crystals. These findings are important for understanding and predicting the stability of amorphous drugs.
During the seminar, we will discuss the educational pathways and the career opportunities provided by the B.S. degree program in Pharmaceutical Science at York College.