Acquisition of Analytical Ultracentrifuge for the Study of Interaction of Surfactants and Polymers

ABSTRACT

CTS-9905217

Somasundaran, P.

Columbia University

A large number of aqueous and non-aqueous based systems in the nature and commerce contains one or more polymer and surfactants in the same solution or suspension. In such systems, interactions between polymers and surfactants, as well as changes resultant in properties conferred by any 'complex' formed by such interactions, can be of considerable importance in biological systems such as membranes and carriers (lipid transport), and commercial systems of foods, pharmaceutics, cosmetics, detergents and various other chemical systems. Many commercial products containing such mixtures has been widely used in different areas, but formulation of these products has mainly depended on trial and error tests. Clearly a full knowledge of the interaction characteristics of relevant polymers and surfactants will greatly aid the development of efficient products. Toward this purpose we propose to acquire an analytical ultracentrifuge comprising two optical systems for determining concentration distribution. Two important types of experiments can be performed with the analytical ultracentrifuge: in the sedimentation equilibrium experiments, a steady state condition is allowed to develop in which the tendency of a sample to sediment in the centrifugal field is counterbalanced by its tendency to diffuse against the concentration gradient so established. In the sedimentation velocity experiment, the speed with which a molecule moves toward the bottom of the cell is determined. This yields the sedimentation coefficients, and the diffusion coefficient D, which can be related to the molecular weight and the frictional coefficient related to the shape of macromolecules ranging in size from several thousand to tens of millions of dolton. Studies that can be conducted on the dynamics of interactions of polymers and surfactants in solutions using this technique would provide a quantum leap in our knowledge of the behavior of surfactants, polymers and their mixtures. We will be able to use analytical ultracentrifuge also in our study of surfactant, mixtures to understand the relationship between surfactant type, mixing ration and the shape, composition and structure of mixed micelles. Another application will be in our work on coating and coagulation of nanosized particles for preparation of nanocomposites that could lead to significant advance in composite fabrication. Recently, we have expanded our studies of surface adsorption phenomena into the area of polymer (protein)-surfactant mixture systems. The unique capability of the Analytical Ultracentrifuge to provide direst information on the molecular weight distribution of polymer (protein)-surfactant complexes is invaluable in the study of Nan-size polymer-surfactant domains and the solubility of these domains. The acquisition of an Analytical Ultracentrifuge System will thus great enhance the capabilities of Columbia University NSF IUCR Center for Advanced Studies in Novel Surfactants, and will enable us to explore the rapidly expanding frontiers of surfactant and polymer applications.