Fourier Transform Infrared Spectroscopy in Colloid and Interface Science

Abstract

This chapter reviews the wide range of colloidal systems amenable to investigation by FT -IR spectroscopy. Molecular level information about the interactions of amphiphilic substances in aggregates such as micelles, bilayers, and gels can be obtained and related to the appearance and stability of the various phases exhibited. The interactions of polymers, surfactants and proteins with interfaces, which substantially modify the solid -liquid or liquid -air interface in many important industrial and natural processes, can also be monitored using FT -IR.Several themes of the application of FT-IR to studies of colloidal particles and interfaces have appeared over the last decade or so. The purpose of this chapter is to attempt to draw together examples of such research topics for both the practicing spectroscopist and workers in the field of colloid and surfactant science. Major advances have been made in recent years in the areas of spectroscopic data handling (which have affected the "look" and "feel" of the analytical laboratory in general) and sample handling (various new optical accessories). These advances have made FT-IR a truly accessible technique, with tremendous potential for application to research in areas of considerable economic, as well as fundamental, importance.Synthetic surfactants are ubiquitous in the modem world, appearing in a wide variety of consumer cleaning products, in foods and cosmetics, and in industrial products and processes such as metal cleaning and enhanced oil recovery. The design of novel surfactant -based products or processes featuring "improved" performance or decreased environmental impact requires an understanding of the relationship of molecular structure to surfactant phase behavior. In the case of "natural amphiphiles" such as the phospholipids, a single phase, the bilayer, is of paramount importance. Significant advances in the understanding of the molecular forces which stabilize these aggregates have been made recently using vibrational spectroscopy. In nature, membrane bilayers incorporate significant amounts of additional substances such as proteins and cholesterol. Although more complex, such systems are also beginning to yield to spectroscopic analysis. Besides being of fundamental interest, membrane bilayer chemistry affects areas of considerable economic opportunity, considering pharmaceutical chemistry alone.Many of the spectroscopic concepts developed in studies of bilayers are applicable to other molecular aggregates such as surfactant miceUes and gels. The

Kinetic studies of attachment and re-orientation of octyltriethoxysilane for formation of self-assembled monolayer on a silica substrate

“…Further, the above peaks had undergone narrowing with time. These red shifting and narrowing of peaks indicate a dense and solid packing of octyl groups due to rearrangement of the attached molecules [7,[40][41][42][43]. Increasing peak areas of asymmetric peaks are observed with increase in silanization time.…”

Mechanisms of siderophore sorption to smectite and siderophore-enhanced release of structural Fe3+

“…Numerous studies have employed FTIR to assess the conformation of organic molecules at interfaces. Changes to the conformation of these molecules as well as intermolecular interactions between them result in changes to the positions, widths, and heights of the asymmetric and symmetric bands t(C-H) bands (e.g., Scheuing, 1990;Vaia et al, 1994). For example, Zhu et al (2005) found that when alkylammonium molecules are sorbed to smectite, the t(CH 2 ) bands occur at low frequencies relative to the position of these bands in solid-state reference samples.…”

Solubilization in nonionic reverse micelles in carbon dioxide

“…Unfortunately, the absorptions of C 0 2 itself obscure these modes. However, it has been suggested (Scheuing, 1990) that shifts in the position of the bending mode…”