A Unified Approach to Surfaces

Our knowledge of chemistry and physics of surfaces has taken major strides in the past three decades. The fundamental knowledge of structure, properties and behavior of surfaces has contributed immensely to the solutions of problems not only in engineering, but also in agriculture, biology, medicine and pharmacy. The universality of surface science was recognized by the Board of Regents who established the Interdisciplinary Center for Surface Science and Engineering at the University of Florida in 1985.

It should be recognized that the principles governing the behavior of molecules at surfaces are the same for both engineering and biomedical systems. Presently, faculty members from Colleges of Agriculture, Arts & Sciences, Engineering, Medicine, Pharmacy and Veterinary Medicine participate in the activities of the center. These colleagues have combined their efforts to develop a unified base of knowledge of surface science and to delineate the mechanisms by which surface interactions of molecules influence the properties of engineering and biomedical systems.

Project I –       Kinetics of Mixed Ionic/Nonionic Micelles

The kinetics of micelle breakup and formation has been shown to be an important factor in several interfacial phenomena.  An ongoing research goal of this group has been to develop a methodology for characterizing the stability of a surfactant micelle in order to tailor micelle lifetimes for optimum performance in various technological processes.  This project involves the mixing of anionic, cationic, and nonionic surfactants in order to achieve very long micelle lifetimes in the order of seconds to minutes.

Project II –     Kinetics of Gemini Micelles

This project has the same ultimate goal as Project I, but the focus of research in this project is a new type of dimeric or “Gemini” surfactant.  These Gemini surfactants are made up of two surfactant monomers linked at the polar group of each monomer by a linker, or spacer, moiety.  The length and makeup of this spacer moiety dictates the flexibility of each monomer in the dimeric molecule.  The result is a small molecule with a high diffusion rate, high surface activity, and low critical micelle concentration (CMC). 

 Much of the study on Gemini surfactants has involved thermodynamic properties (e.g. CMC, adsorption energies, area per molecule) of these systems.  Recently, attention has turned to kinetics of association and dissociation of Gemini surfactant micelles.  The slow micellar relaxation time (t₂), the dynamic surface tension, and the diffusion constants for several of these Gemini surfactant systems are being studied.

Project III –    Effect of Soap Concentration, Mixed Chain Length, and Degree of Unsaturation on Fatty Acid pKa

Films of fatty acid salts were studied at various pH values of the solutions.  It was found that there exists a pH where minimum evaporation of water, maximum foamability, maximum foam stability, minimum contact angle on PMMA surface, maximum single-bubble stability, and maximum surface viscosity are observed.  It was also found that this optimum pH value is near the pKa of the fatty acid salts, and that pKa increases as the chain length of the fatty acid salt increases.  Mixing of soap molecules of unequal chain length and increasing the degree of unsaturation decreases the pKa of soap solutions.  Results indicate that premicellar surfactant aggregation and molecular association well below the cmc of the soap considerably affects ionization of the polar group.  

Project IV –    Manufacture of Low-Density Gypsum Boards by Addition of Surfactant

This project explores the possibility of decreasing the density of gypsum boards by the addition of surfactants and the formation of solid foam.  Surfactant molecules will be used to stabilize the air bubbles within the gypsum slurry, preventing the bubbles from collapsing or expanding during the drying process.  An x-ray tomography unit will be used to produce a three-dimensional image of the internal structure of the foam.  Mechanical strength tests will determine the optimum bubble size distribution within the gypsum boards.

Project V –      A Study of Calcium Carbonate Crystal Formation Onto Fatty Acid Monolayers

Calcium carbonate can be used to create particles with a hard shell and a liquid interior.  The idea is that the outer shell of these particles can protect the interior from the external medium.  Core-shell particles such as these could conceivably be loaded with drugs for use as pharmaceuticals or for direct injection into the body.  One way to create these calcium carbonate shells is by growing them onto a fatty acid monolayer.

Project VI –    Molecular Mechanisms of Spontaneous Emulsification to Produce Nanoemulsions

Our group has developed a method to quantitatively determine the spontaneity (S) of the spontaneous emulsification process using a laser diffraction particle size analysis technique.  The method was experimentally tested by studying the rate of increase of the specific interfacial area (cm² mL^-1 s^-1) and the equilibrium specific interfacial area for different systems formed by the surfactant Brij 30 dissolved in linear alkyl oils (C₈-C₁₆) when brought in contact with ultrapure water.  Experimental results confirm the effectiveness of the method, and they also suggest that the oil chain length of the linear alkyl oils has an important effect on the driving force of the spontaneous emulsification process in these systems. A molecular spontaneous emulsification mechanism has been developed for the systems studied.

Project VII –   Blood Compatible Nanosystems to Detoxify Drug Overdose Victims

This project focuses on nanoparticulate systems for toxicity reversal of overdosed drugs. Drug toxicity in humans as a result of therapeutic miscalculation, illicit drug usage, or suicide attempt is a major health care problem in the United States. The vast majority of life threatening drug intoxications do not have specific pharmacological antidotes to reverse their adverse effects. Our objective is therefore to synthesize a series of novel nanobioparticles that effectively reduce the free blood concentration of toxic drugs.

^Important  Please Note:  This web page does not represent all of the research being conducted at the CSSE.  It is simply a presentation platform for those CSSE members who wish to use the WWW to share their results with others.  Notice to CSSE members:  DO NOT post unpublished or undocumented data and results to this web page without taking the appropriate security precautions.