Adsorption behavior, solid surface polymer

Polymer Adsorption. A review of the theory and measurement of polymer adsorption points out succinctly the distinquishing features of the behavior of macromolecules at solid - liquid interfaces (118). Polymer adsoiption and desorption kinetics are more complex than those of small molecules, mainly because of the lower diffusion rates of polymer chains in solution and the "rearrangement" of adsorbed chains on a solid surface, characterized by slowly formed, multi-point attachments. The latter point is one which is of special interest in protein adsoiption from aqueous solutions. In the case of proteins, initial adsoiption kinetics may be quite rapid. However, the slow rearrangement step may be much more important in terms of the function of the adsorbed layer in natural processes, such as thrombogenesis or biocorrosion / biofouling caused by cell adhesion. 

Polymers can be confined one-dimensionally by an impenetrable surface besides the more familiar confinements of higher dimensions. Introduction of a planar surface to a bulk polymer breaks the translational symmetry and produces a pol-ymer/wall interface. Interfacial chain behavior of polymer solutions has been extensively studied both experimentally and theoretically [1-6]. In contrast, polymer melt/solid interfaces are one of the least understood subjects in polymer science. Many recent interfacial studies have begun to investigate effects of surface confinement on chain mobility and glass transition [7], Melt adsorption on and desorption off a solid surface pertain to dispersion and preparation of filled polymers containing a great deal of particle/matrix interfaces [8], The state of chain adsorption also determine the hydrodynamic boundary condition (HBC) at the interface between an extruded melt and wall of an extrusion die, where the HBC can directly influence the flow behavior in polymer processing. 

Although this book significantly differs from the earlier Colloid Chemistry textbook, it nevertheless focuses on the specifics of educational and research work carried out at the Colloid Chemistry Division at the Chemistry Department of MSU. Many results presented in this book represent the art developed in the laboratories of the Colloid Chemistry Division, in the Laboratory of Physical-Chemical Mechanics (headed by E.D. Shchukin since 1967) of the Institute of Physical Chemistry of the Russian Academy of Science, and in other research institutions and industrial laboratories under the guidance of the authors and with their direct participation. Special attention is devoted in the book to the broad capabilities that the use of surfactants offers for controlling the properties and behavior of disperse systems and various materials due to the specific physico-chemical interactions taking place at interfaces. At the same time the authors made every effort to avoid duplication of material traditionally covered in textbooks on physical chemistry, electrochemistry, polymer chemistry, etc. These include adsorption from the gas phase on solid surfaces (by microporous adsorbents), the structure of the dense part of the electrical double layer, electrocapillary phenomena, specific properties of polymer colloids, and some other areas. 

In this short review, we have presented some results on the behavior of polymer solutions close to surfaces in the context of adhesion phenomena. The emphasis has been placed on the interaction between two flat parallel solid surfaces induced by a polymer solution and more specifically on the bridging effect between the surfaces due to the polymer. Two types of interactions between the surface and the polymer have been considered grafting and adsorption. 

The solid surface can cause breakdown of the adsorbed polymer. For example, immediately after adsorption of the polyesters on quartz glass, aluminum oxide, and other hydrated surfaces, hydrolysis is observed [31]. Such behavior is understandable for these substances given that upon adsorption the polar group of the ester must be in direct contact with the solid body if there is no steric hindance. It is... 

The adsorption of polymers at the liquid/liquid interface is somewhat different from that at the solid/liquid interface as the polymer can penetrate both phases, x determines the adsorption behavior of polymers at liquid/liquid interfaces. The presence of the polymer at the interface between the two immiscible liquids lowers the surface tension. Determination of the adsorption isotherm (see Section IX.B) is more straightforward compared to particulate dispersions as surface tension measurements, interpreted using the Gibbs equation, can be used to give accurate adsorbed amounts. 

Before dealing with the adsorption behavior of polymer-surfactant systems, we outline briefly, the main features of polymer and surfactant association in aqueous solution. In another section, we analyze the major differences existing between the adsorption of a polymer and a surfactant at the solid surface. Further sections will discuss in more detail the adsorption pattern of both the polymer and the surfactant when they are mixed together in solution. 

Polymers with which we will deal throughout this chapter are water soluble. They can be either ionic or nonionic. Some of them are synthetic, others are of biological origin (proteins, for instance). Both homopolymers and heteropolymers exist. Some polymers own amphiphilic monomers that induce surface-active properties to the whole polymeric structure. Water plays a very important role in determining the polymer properties in solution. The properties are also greatly modified by the addition of salts or by a pH modification. Frequently encountered nonionic polymers in polymer-surfactant interactions and their subsequent adsorption behavior at solid surfaces are poly(ethylene oxide) (PEO), poly(vinyl pyrrolidone) (PVP), polyacrylamide, and poly(vinyl alcohol). 

Polymer and surfactant do not interact with each other in solution. Nevertheless they adsorb both at the solid surface. As a consequence, both polymer and surfactant adsorption behavior is modified by the presence of the other. This kind of behavior can be treated in terms of adsorption competition between the polymer and the surfactant for the same solid surface. Very often, such situations are encountered for polymer and surfactant owning the same electrical charge and adsorbing onto an oppositely charged solid surface. 

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