Each of these projects is a candidate worthy of CHEM 495 or CHEM 498 research credit.
Polymer Encapsulated Reverse Micelles (PERMS)
Polymer Encapsulated Reverse Micelles (PERMs) are nanometer-sized droplets of liquid water completely surrounded by a layer of amphiphillic surfactant molecules which are, in turn, embedded in a solid hydrophobic matrix of polystyrene. These PERMs provide an excellent system for measuring intra-micellar water dynamics especially because of the polystyrene neatly isolates and immobilizes the micelles in rigid structures. NMR methods have long been used to elucidate molecular structure and dynamics of Reverse Micelles (RMs) in solution, that is, suspended in liquid hydrocarbons. Measurement of such liquid RM systems can been confounded by the motion of the micelles themselves which is effectively quenched in PERM systems.
How are water dynamics modified by the extreme confinement inside of reverse micelles?
Molecules Encapsulated in PERMs - It is possible to introduce small molecules into the aqueous phase of PERMs and to examine their behavior under the conditions of confinement created by the PERM structure. Considering that Reverse Micelles (RMs) with a diameter of two to four nanometers contain somewhere around 150 to 1,000 water molecules there is a limit to the number of solute molecules that can be contained inside of one. Consider further that neat water exhibits a concentration of 55 M, that is, one liter of water contains 55 moles of water molecules. These together imply that with a one molar solution of salt the inside of a RM has only three to twenty (dissociated salt molecules) inside of it.
Do solvated systems of such small volume behave like bulk solutions or not? Why?
Sodium Ion and Surfactant Dynamics in PERMs - Inside the water pore of a representative PERM the polar head group of the surfactant (AOT, sodium dioctylsulfosuccinate) contributes considerable ionic strength in terms of sodium cations and sulfate anions. In fact, the local concentration can exceed eight molar in sodium. Further, depending upon the synthesis details there simultaneously exist a relatively small number of water molecules per sodium ion creating a unique environment for studying ionic solute-solvent interactions.
Do the water molecules and sodium ions in this environment exhibit behavior different from bulk solution?
Instrument Design & Development
Isothermal Microcalorimeter Interface and Control Design -
The Two-Drop Calorimeter is a brilliant scientific instrument. It is an isothermal microcalorimeter and can measure can exceedingly small heat of reaction in very small volume. Our microcalorimeter has been used to measure 10-5 Joules in a reaction consisting of two 50 uL drops of reactants. It has also been used to measure the basal metabolism rate of living common house flies (musca domesticata). The rate is around 200 uW for a roughly 20 mg fly.
Unfortunately, the microcalorimeter is suffering from age. Actually, the instrument itself is working quite well. It is the computer that is suffering. You see, the instrument uses an obsolete analog-digital interface board that prevents us from upgrading the host computer or its operating system. The company has been sold twice over since the instrument was purchased some years ago and all we can get out of the new manufacturer is "Just buy a new fancy one." No thanks! Our instrument works great and we're going to build a new interface for it.
The project is already underway. We've decided to use a Linux computer to control the instrument and to create a web-browser-based interface that will permit the instrument to be used anywhere the Internet exists (and when we provide permission through our firewall). There's still much work to do.
If the terms Apache Web Server, C Programming Language, Unix Daemon, User Interface make your pulse quicken then we need to speak.
The Smell-O-Scope - Flavors & Fragrances
Gas Chromatography (GC) & Olfactometry - text
NMR Instrument Design & Development
Magic Angle Rotation (MAR) NMR Spectroscopy - is a highly specialized and experimentally challenging form of solid-state NMR spectroscopy. It is an extension of Magic Angle Spinning (MAS) spectroscopy which has been extremely successful at revealing interesting chemistry in solid materials (as contrasted with liquids) and has served as very fertile ground for the application of the principles of quantum mechanics.
Biological NMR
The Dynamics of DNA
Cryogenic NMR
The Surface Structures & Dynamics of Elemental Silicon and of Silica - test
Would you like to build apparatus and perform experiments at temperatures as low as 4 K?
High Pressure Liquid Chromatography (HPLC) Methods Development
tag - text
A set of styrene-divinylbenzene-based PERMs in the making.
An array of raw polymer and PERM monoliths representing a wide range of sample composition and synthesis conditions.
Cartoon depicting the synthesis of PERMs. In the left panel reverse micelles are formed in the liquid phase polymer precursors. These precursors are transformed into a solid polymer using a free radical initiator and either heat or UV light which results in the permanent immobilization of the micelles in the solid.
The surface of a fractured PERM as seen with an Atomic Force Microscope (AFM). The surface appears to exhibit the depressions (pores?) remaining after the water and surfactant molecules have been washed off.
A piece of cake showing the appearance of the embedded fruit and nuts when the cake is sliced open. Compare to the above PERM surface.
The Isothermal Microcalorimeter is shown here with its old and new computer controllers. The Windows-based computer is on the left and Linux-based computer is on the right; the calorimeter itself is located at the far left.
A "Perfumer's Organ" in La Grasse, France where fragrances are composed from a (large) number of pure substances.
A "Fragrance Stand" in Bronx, NYC where fragrances are composed on demand. The most popular fragrances are purported to be "Wife Obey Me" and "Husband Obey Me."
The Smell-O-Scope, a gas chromatograph with ofactometric accessory port, developed in this laboratory and in use.
A Magic Angle Spinning (MAS) system (in the movie above) observed with a stroboscopic light operating at 3.5 kHz and designed to "stop" the motion of of the rotor in the center of the apparatus. It can be seen that the rotor's speed is not constant but varies on the timescale of seconds. This variation in speed is slow enough that it does not interfere with the coherent averaging and line narrowing provided by MAS in the NMR experiment.
A experimental Magic Angle Rotation (MAR) system (in the movie above) is observed in a similar fashion. It can be seen in this case that rotor system is subject to much greater and faster variations in its rotational speed. These variations are significant enough to interfere with the coherent averaging provided by MAR and cause the loss of observable magnetization in the NMR experiment.
