Welcome to the Frank Group!
Contact Info
Stauffer III, Room 105
381 North-South Mall
Stanford, CA 94305
Office: (650) 723-9140
Lab: (650) 723-0763
CPIMA: (650) 736-8903
Fax: (650) 723-9780
Chemical Engineering at Stanford
Research Statement
Structure and Dynamics of Polymers in Constrained Geometry
The properties of ultrathin polymer films are often different from their bulk counterparts. We use spin casting, Langmuir-Blodgett deposition, and surface grafting to fabricate ultrathin films in the range of 100 to 1000 Angstroms thick. Macromolecular amphiphiles are examined at the air-water interface by surface pressure, Brewster angle microscopy, and interfacial shear measurements and on solid substrates by atomic force microscopy, FTIR, and ellipsometry. A vapor-deposition-polymerization process has been developed for covalent grafting of poly(amino acids) from solid substrates. FTIR measurements permit study of secondary structures (right and left-handed alpha helices, parallel and anti-parallel beta sheets) as a function of temperature and environment.
Interface Science of Biomolecular Materials
The cell membrane is a wonderfully complex structure having a phospholipids matrix with a wide variety of associated and integral membrane proteins. We are exploring highly simplified analogues of the cell membrane for possible applications in bioanalytical devices. Vesicles or liposomes of phospholipids are prepared by sonication or membrane extrusion and characterized by dynamic light scattering. The kinetics of adsorption of these vesicles on a solid substrate followed by fusion to form a continuous supported bilayer is followed by the quartz crystal microbalance with dissipation. This instrument allows determination of both the mass deposition as well as the viscoelastic coupling of the adsorbed film with the surrounding fluid. Fluorescence recovery after pattern photobleaching is used to monitor the lateral diffusivity of labeled lipids.
Polymer Development of an Artificial Cornea Based on Polymer Hydrogels
A broadly interdisciplinary collaboration has been established with the Department of Ophthalmology in the Stanford School of Medicine. We have designed and synthesized a fully interpenetrating network of two different hydrogel materials that have properties consistent with application as a substitute for the human cornea: high water swellability up to 85%,tensile strength comparable to the cornea, high glucose permeability comparable to the cornea, and sufficient tear strength to permit suturing. We have developed a technique for surface modification with adhesion peptides that allows binding of collagen and subsequent growth of epithelial cells. Broad questions on the relationships among molecular structure, processing protocol, and biomedical device application are being pursued.
Improving Processability of Biopolyesters for Sustainable Construction Materials
Due to continued concern over environmental impact and sustainability of materials, poly(hydroxyalkanoates) (PHAs), a family of bacterial polyesters, have been growing in popularity. PHAs have properties comparable to the conventional plastic polypropylene (PP), with the added benefits of biodegradability, biorenewability, and no toxicity. However, they have a narrow thermal processing window and poor mechanical properties that limit its application. In collaboration with the Civil Engineering Department, we are focused on enhancing the processability of PHAs for applications in construction materials via chemical modification, physical blending, processing additives, and understanding thermodynamics to optimize processing conditions. Specifically, we use extrusion, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and more to produce and characterize biodegradable PHA foams for insulation and structural applications.
Structure-Property Relationships of Polyelectrolytes for Energy Applications
Energy demands are growing and polymers play an integral role in advancing energy generation technologies. Currently we focus on synthesizing and characterizing polymer electrolyte membranes for fuel cells: both acidic and alkaline environments. We use various synthesis methods and processing techniques to produce polyelectrolyte films with a focus on composite materials that have nanometer scale features. Small-angle x-ray scattering, differential scanning calorimetry, thermal gravimetric analysis, conductivity measurements, FTIR, and NMR are the tools used to analyze the relationship between how the material structure impacts its properties from the nanometer scale all the way up to understanding its macroscopic performance.