Eric Jayjock

Ph.D. Student

B.S. Chemical Engineering,
Pennsylvania State University, 2001.

My research is centered around quantitatively understanding the formation of nanoparticles for applications in the pharmaceutical industry with an emphasis on manufacturing techniques. This discipline involves the combination of Molecular Dynamic modeling (MD), Computational Fluid Dynamics modeling (CFD) and experimental work to decipher the mechanism of creation of nanoparticles for novel production paths. I'm very excited to have a chance to do participate in a very young field that is sure to have an immeasurable impact on the way we live in the years to come.

Office: Engineering Building C-149
Phone: 732-445-2049
Email: ejayjock@soemail.rutgers.edu

Yangyang Shen

Ph.D. Student

B.S. Polymer Science and Engineering,
Beijing University of Chemical Technology, 2000

We investigate the mechanism by which aqueous trisiloxane solutions advance over hydrophobic surfaces (i.e. the mechanism of "superspreading"). I'm focusing on the molecular dynamics simulation of superspreading of surfactant solutions on a hydrophobic surface. The solid substrate is modeled as an atomic lattice with thermal oscillations,and the solvent as an atomic Lennard-Jones liquid, with solvent-solid interactions chosen to give partial wetting behavior.We compare the behavior of two different systems: freely jointed FENE chains of different length, and simple ``T-shaped'' surfactant molecules with FENE and bond-benging forces. To study wetting phenomena, we simulate a complete spreading experiment at miscroscopic scales, in which an equilibrated drop of model surfactant solution is placed near the solid and allowed to spread under the action of specified intermolecular potentials, taken to have Lennard-Jones form with adjustable strengths. In the preliminary results, we showed that addition of the ``T-shaped'' surfactant molecules promoted rapid spreading.

Office: Engineering Building C-149
Phone: 732-445-2049
Email: yyshen@soemail.rutgers.edu
Personal website

JeongYong Lee

Ph.D. Student

Co-advised with Prof. Jing Li and Visiting Professor Arthur Chester

B.S. Chemistry, 1994
M.S. Solid State Chemistry, 1996
Yonsei University, KOREA.

Ashish Misra

Ph.D. Student

B.S., Chemical Engineering,
University of Bombay, 2002

Surfactants (Surface active agents) are a class of compounds that contain hydrophilic and hydrophobic groups of atoms in the same molecule. This allows them to assemble at an oil-water or air-water interface with the hydrophobic atoms pointing away from water. This self assembly of surfactant molecules is responsible for a reduction in the surface tension at such interfaces. Surfactants with some charged groups are ionic in nature while those with uncharged groups are nonionic. Non ionic surfactants are of practical importance in a variety of applications including pesticides, cosmetics, etc due to their low toxicities compared to ionic surfactants.
Due to certain favorable interactions between nonionic surfactants with different structures, it is found that mixtures of some of these surfactants have a better effect on surface tension reduction as compared to the individual molecules themselves. This beneficial interaction is termed synergism. We are investigating synergistic effects between nonionic surfactants at an air-water interface using molecular dynamics simulations. The various species in the simulations interact via the Lennard-Jones (6-12) potential. Water molecules are represented as monomers and the surfactants are represented by a qualitative model as a composite molecule composed of hydrophilic and hydrophobic atoms. We vary the surfactant structures and interaction coefficients between various species in the simulation and see the effect they have on surface tension reduction for the individual surfactants and combination of surfactants.

Office: Engineering Building C-149
Phone: 732-445-2049
Email: misra@eden.rutgers.edu

Bo Li

Research Associate

Ph.D., Chemical Engineering,
University of Cincinnati, 2002.

Surface Characterization of Aspirin Crystal Planes using Molecular Dynamics Simulations

Crystal morphology and growth rates are directly determined by the binding energies of their constituent molecules, i.e. the energy released when a molecule is attached to the growing surface (Hartmann, 1955). Dissolution studies of different aspirin crystal planes have revealed that the dissolution velocities of aspirin crystallized from different solvents may be due to the extent of expression of different crystal planes (Danesh, 2000). Other studies (Watanabe, 1982, Meenan 1997) have shown that aspirin crystals reveal plate shaped form (where crystal plane 001 has optimum growth) and needle-shaped form (where crystal plane 100 has optimum growth) as a result of crystallization of from ethanol and hexane, respectively. We are interested in understanding the main mechanisms by which solvent and additives affect crystal surface characteristics. Molecular crystal models of selected drug compounds (e.g. aspirin) are constructed using the latest materials numerical simulation platform - Materials Studio. COMPASS, the latest molecular mechanics force field for condensed-phase material simulations, is used to represent the atomic interactions in the target systems. Surfactant molecules with different composition and functional groups are introduced onto the crystal/solvent interfaces at different concentrations.

Bodhisattwa Chaudhuri

Research Associate

Ph.D., Mechanical Engineering,
New Jersey Institute of Technology, 2000

The storage, flow and processing of cohesive granular material are vital in the food, pharmaceutical, agricultural, building and mining industries. Our research involves the development of a discrete element method (DEM) based numerical model to understand the constitutive behavior of the cohesive powder. We consider the granular material as a collection of frictional inelastic spherical particles. Each particle may interact with its neighbors or with the boundary only at contact points through normal and tangential forces. We introduce a normal cohesive force on top of the normal force calculated from the latching spring model for particle-particle or particle-wall collisions. Tangential forces from the collisions are calculated employing Walton's incrementally slipping model. Tangential force obeys Coulomb's law, where its magnitude if more than the product of the normal force and the coefficient of static friction, sliding occurs with a constant coefficient of dynamic friction.

The effect of cohesion in the mixing processes is also under our investigation. DEM based simulations are used to analyze the mixing and segregation of cohesive powder systems, handled inside the rotating drum. Currently we are investigating mixing of two different powders of same size. Our goal is to check the same for heterogeneous systems. We plan to use DEM simulations to investigate the effect of cohesion on mixing process, inside double cone and tote blenders. We will set a baffle inside the blender and evaluate the effect of its size and orientation on mixing and segregation.

Office: Engineering Building C-123
Phone: 732-445-6708
Email: bodhisch@soemail.rutgers.edu
Personal website