Interphase chemistry

Centre for Surface Chemistry and Catalysis, Department of Interphase Chemistry, Faculty of Agricultural and Applied Biological Sciences, Katholleke Universitelt Leuven, Leuven, Belgium... 

This paper wiU build on previous reviews which have sought to explore the marmer in which surface analysis methods can be purposefully employed to understand adhesion phenomena [4—6], with an emphasis on the elucidation of interphase chemistry. The rationale behind such an approach is that it is this critical region of a polymer/metal or polymer/polymer couple that will influence the performance of the overall system, be it the durability of an adhesive joint or the corrosion protection performance of an organic coating. 

Department of Interphase Chemistry Kasteelpark Arenberg 23 3001 Leuven Belgium... 

Pereira-Nabais C., Swiatowska J., Chagnes A., Ozaneun F., Gohier A., Tran-Van R, Cojocaru C.-S., Cassir M., Marcus P. Interphase chemistry of Si electrodes used as anodes in li-ion batteries, Appl. Surf. Sci. 2013, 266, 5-16. 

Adhesion is a consequence of the chemical or physical interaction between two surfaces, one of which is a solid and the other a liquid, temporarily more mobile. As a consequence of the way in which adhesion is achieved practically. the interface or interphase region, where the bonds responsible for adhesion occur, is buried below many im, or even mm, of solid sub.stratc and solidified (generally crosslinked) polymer. The dimensions of the interphasc region are likely to be of the order of nm at the most (unless an extended mechanical interphase is present of the type found in the adhesive bonding of anodized aluminum alloys) so that direct examination of interphase chemistry is best considered as an exercise in the analysis of a deeply buried interface. This situation is encountered frequently by those working in microelectronics and in corro,sion and oxidation research. Removal of material is invariably ac-... 

From the above examples it can be seen that the locus of failure generated by a mechanical test, either before or after environmental exposure is an uncertain route to exposing surfaces that will allow the elucidation of interface or interphase chemistry directly. In the following sections, a number of methods are described that allow the interfacial chemistry of adhesion to examine directly by analytical methods. They fall into two categories those in which a real interface is sectioned to allow surface analysis and other methods to probe the interfacial region, and those which make use of model systems, often in the form of very thin (<2 nm) films of adhesive where the interphase chemistry is directly accessible by surface analysis methods. 

The concept that by carrying out a surface analysis on a model specimen one can obtain direct access to the interphase chemistry is a potentially very exciting and rewarding idea. The interaction of PMMA with various metals (as exemplified hyO Fig. 10.14 above) has been studied in some detail using high resolution XPS (Leadley and Watts 1997). In this work the manner in which PMMA formed specific interactions with oxidized metal surfaces was studied by the nature of the fine structure in the XPS spectrum. In this manner, it was possible to show that the polymer formed hydrogen bonds with oxidised silicon (an acidic substrate), a bidentate structure with oxidised aluminum (an amphoteric substrate) and would undergo acyl nucleophilic attack with oxidised nickel (a basic substrate). 

The performance of a product where adhesion plays a role is determined both by its adhesive and cohesive properties. In the case of silicones, the promotion of adhesion and cohesion follows different mechanisms [37]. In this context, adhesion promotion deals with the bonding of a silicone phase to the substrate and reinforcement of the interphase region formed at the silicone-substrate interphase. The thickness and clear definition of this interphase is not well known, and in fact depends on many parameters including the surface physico-chemistry of... 

This involves knowledge of chemistry, by the factors distinguishing the micro-kinetics of chemical reactions and macro-kinetics used to describe the physical transport phenomena. The complexity of the chemical system and insufficient knowledge of the details requires that reactions are lumped, and kinetics expressed with the aid of empirical rate constants. Physical effects in chemical reactors are difficult to eliminate from the chemical rate processes. Non-uniformities in the velocity, and temperature profiles, with interphase, intraparticle heat, and mass transfer tend to distort the kinetic data. These make the analyses and scale-up of a reactor more difficult. Reaction rate data obtained from laboratory studies without a proper account of the physical effects can produce erroneous rate expressions. Here, chemical reactor flow models using matliematical expressions show how physical... 

This review has been restricted mainly to clarification ofthe fundamentals and to presenting a coherent view ofthe actual state of research on voltaic cells, as well as their applications. Voltaic cells are, or may be, used in various branches of electrochemistry and surface chemistry, both in basic and applied research. They particularly enable interpretations of the potentials of various interphase and electrode boundaries, including those that are employed in galvanic and electroanalytical cells. 

The first of these assumptions, generally accepted in macromolecular chemistry [1,3], is correct enough when considering the propagation reaction under copolymerization of the majority of monomers. Simple estimates reported in paper [74] support the correctness of the second assumption. As for the third one, it is true, strictly speaking, only under 0-conditions. The conformational statistics of macromolecules in a thermodynamically good solvent is known [30] to differ from the Gaussian one. Nevertheless, this distinction may hardly influence the qualitative conclusions of the simplest theory of interphase copolymerization. To which extent the account of the excluded volume of macromolecules will affect quantitative results of this theory, may be revealed exclusively by computer simulations. 

The term chemistry in interphases was first introduced in the field of reverse-phase chromatography [41], In 1995 Lindner et al. transferred the concept to the area of transition metal catalysis [42] and in a recent review the concept is explained in detail [43], The interphase is defined as a region within a system in which the stationary and a mobile component penetrate on a molecular level without the formation of a homogeneous mixture. In these regions the reactive centre on the stationary phase... 

Kleijn, J. M. and van Leeuwen, H. P. (2000). Electrostatic and electrodynamic properties of biological interphases. In Physical Chemistry of Biological Interfaces. eds. Baszkin, A. and Norde, W., Marcel Dekker, New York, pp. 49-63. 

Escher, B. and Sigg, L. (2004). Chemical speciation of organics and metals at biological interphases. In Physicochemical Kinetics and Transport at Biointerfaces. eds. van Leeuwen, H. P. and Koster, W., Vol. 9, IUPAC Series on Analytical and Physical Chemistry of Environmental Systems, Series eds. Buffle, J. and van Leeuwen, H. P., John Wiley Sons Ltd, Chichester, pp. 205-269. 

Model of a supramolecular structure of polymolecular ensembles or clusters, determined by interaction and mutual arrangement of the forming molecules. At this level, the specific mechanisms of supramolecular chemistry, including molecular recognition, self-assembly, etc. [4] can be allocated. In most cases, it is possible to limit this area to objects with the sizes under 1 to 2 nm, since further increase in the sizes admits application of statistical concepts like phase and interphase surface. 

The study and application of composite materials are a truly interdisciplinary endeavor that has been enriched by contributions from chemistry, physics, materials science, mechanics and manufacturing engineering. The understanding of the interface (or interphase) in composites is the central point of this interdisciplinary effort. From the early development of composite materials of various nature, the optimization of the interface has been of major importance. While there are many reference books available on composite materials, few of them deal specifically with the science and mechanics of the interface of fiber reinforced composites. Further, many recent advances devoted solely to research in composite interfaces are scattered in different published literature and have yet to be assembled in a readily accessible form. To this end this book is an attempt to bring together recent developments in the field, both from the materials science and mechanics perspective, in a single convenient volume. 

In 1976 he was appointed to Associate Professor for Technical Chemistry at the University Hannover. His research group experimentally investigated the interrelation of adsorption, transfer processes and chemical reaction in bubble columns by means of various model reactions a) the formation of tertiary-butanol from isobutene in the presence of sulphuric acid as a catalyst b) the absorption and interphase mass transfer of CO2 in the presence and absence of the enzyme carboanhydrase c) chlorination of toluene d) Fischer-Tropsch synthesis. Based on these data, the processes were mathematically modelled Fluid dynamic properties in Fischer-Tropsch Slurry Reactors were evaluated and mass transfer limitation of the process was proved. In addition, the solubiHties of oxygen and CO2 in various aqueous solutions and those of chlorine in benzene and toluene were determined. Within the framework of development of a process for reconditioning of nuclear fuel wastes the kinetics of the denitration of efQuents with formic acid was investigated. 

Let us recall the micellar aqueous system, as this procedure is actually the basic one. The chemistry is based on fatty acids, that build micelles in higher pH ranges and vesicles at pH c. 8.0-8.5 (Hargreaves and Deamer, 1978a). The interest in fatty acids lies also in the fact that they are considered possible candidates for the first prebiotic membranes, as will be seen later on. The experimental apparatus is particularly simple, also a reminder of a possible prebiotic situation the water-insoluble ethyl caprylate is overlaid on an aqueous alkaline solution, so that at the macroscopic interphase there is an hydrolysis reaction that produces caprylate ions. The reaction is very slow, as shown in Figure 7.15, but eventually the critical micelle concentration (cmc) is reached in solution, and thus the first caprylate micelles are formed. Aqueous micelles can actually be seen as lipophylic spherical surfaces, to which the lipophylic ethyl caprylate (EC) avidly binds. The efficient molecular dispersion of EC on the micellar surface speeds up its hydrolysis, (a kind of physical micellar catalysis) and caprylate ions are rapidly formed. This results in the formation of more micelles. However, more micelles determine more binding of the water-insoluble EC, with the formation of more and more micelles a typical autocatalytic behavior. The increase in micelle population was directly monitored by fluorescence quenching techniques, as already used in the case of the... 

The chemical composition of the composite constituents and the interphase is not limited to any particular material class. There are metal-matrix, ceramic-matrix, and polymer-matrix composites, all of which find industrially relevant applications. Similarly, reinforcements in important commercial composites are made of such materials as steel. E-glass, and Kevlar . Many times a bonding agent is added to the fibers prior to compounding to create an interphase of a specified chemistry. We will describe specific component chemistries in subsequent sections. 

The value of the epoxy resins lies in their reactivity with a variety of chemical groups. This enhanced reactivity also means that the surface chemistry of the reinforcement which the epoxies are cured against, can alter the local structure in the interphase regionJl). The most common reinforcement surfaces cured in contact with the epoxies are carbon/graphite fibers, glass fibers, aramid fibers and metal oxides. The surface chemistry of these reinforcement surfaces is quite diverse and in many cases can be the reason for alteration of the interphase epoxy structure as compared to the bulk. 

---