Polymer Adsorption Dynamics

Although surface force theories have been incorporated into the PBE, the current models require experimentally determined parameters such as solid-liquid interface potential, adsorbed polymer layer thickness and particle surface coverage. Future efforts should focus on integrating polymer adsorption dynamics models with P B M s. These models should be extended subsequently for systems involving a mixture of polymers or polymer-surfactant systems. 

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A recent design of the maximum bubble pressure instrument for measurement of dynamic surface tension allows resolution in the millisecond time frame [119, 120]. This was accomplished by increasing the system volume relative to that of the bubble and by using electric and acoustic sensors to track the bubble formation frequency. Miller and co-workers also assessed the hydrodynamic effects arising at short bubble formation times with experiments on very viscous liquids [121]. They proposed a correction procedure to improve reliability at short times. This technique is applicable to the study of surfactant and polymer adsorption from solution [101, 120]. 

In this paper we present results for a series of PEO fractions physically adsorbed on per-deutero polystyrene latex (PSL) in the plateau region of the adsorption isotherm. Hydro-dynamic and adsorption measurements have also been made on this system. Using a porous layer theory developed recently by Cohen Stuart (10) we have calculated the hydrodynamic thickness of these adsorbed polymers directly from the experimental density profiles. The results are then compared with model calculations based on density profiles obtained from the Scheutjens and Fleer (SF) layer model of polymer adsorption (11). 

Tensions of non-relaxed interfaces are sometimes known by the adjective dynamic dynamic surface tension or dynamic inteifacial tension. The term dynamic is not absolute. It depends on De (i.e. on the time scale of the measurement as compared with that of the relaxation process). Some interfacial processes have a long relaxation time (polymer adsorption-desorption), so that for certain purposes (say the measurement of y] they may be considered as being in a state of frozen equilibrium. This last notion was introduced at the end of sec. 1.2.3. Unless otherwise stated, we shall consider static tensions and interfaces which are so weakly curved that curvature energies, bending moments, etc. may be neglected. 

Fig. 13 Velocity dependence of frictional stress for a soft gel sliding on a smooth adhesive solid substrate. The result is based on the molecular picture in Fig. 12, which considers the thermal fluctuation of adsorption and desorption of the polymer chain, (a) The elastic term of the frictional stress of a gel. See text for a description of parameter u. (b) Summation of the elastic term and the viscous term. When v -C Vf, the characteristic polymer adsorption velocity, the elastic term is dominant. At v 2> the viscose term is dominant. Therefore, transition from elastic friction to lubrication occurs at the sliding velocity characterized by the polymer chain dynamics. (Modified from figure 1 in [65])...

The adsorption processes of polymers at liquid interfaces have been modelled, based on very simple assumptions. More sophisticated models contain a large number of independent system parameters, which are rarely available (Douillard Lefebvre 1990). A quantitative description of polymer adsorption which takes into account peculiarities of the adsorbing molecules has still to be developed. It is not possible yet, to describe the polymer adsorption process on the basis of the theory of Scheutjens Fleer (1979, 1980), which does not apply under dynamic conditions. 

Surface chains play a fimdamental role in the interaction processes (adsorption and adhesion) of the cellulose fibrils with other molecules. Such surface interactions play a key role in many areas of science biology (interaction with the plant cell-wall polymers, adsorption of cellulolytic enzymes), industrial (paper and textile industries), and technology (compatibilization and adhesion thermoplastic amorphous matrix on cellulose). Unfortunately, very little information has yet been gathered on the organization, conformation, and dynamics of the surface chains. In fact, few experimental... 

Before discussing the effects that adsorbed polymers have on interactions between surfaces and colloidal bodies, a brief discussion about the kinetic aspects of polymer adsorption phenomena is given. This is an important aspect to consider since papermaking is a dynamic process. At least at low coverage, polymer adsorption tends to be mass-transfer limited, implying that the adsorption rate can be written as follows ... 

This volume consists of four parts. The first part is devoted to theoretical studies and computer simulations. These studies deal with the structure and dynamics of polymers adsorbed at interfaces, equations of state for particles in polymer solutions, interactions in diblock copolymer micelles, and partitioning of biocolloidal particles in biphasic polymer solutions. The second part discusses experimental studies of polymers adsorbed at colloidal surfaces. These studies serve to elucidate the kinetics of polymer adsorption, the hydrodynamic properties of polymer-covered particles, and the configuration of the adsorbed chains. The third part deals with flocculation and stabilization of particles in adsorbing and nonadsorbing polymer solutions. Particular focus is placed on polyelectrolytes in adsorbing solutions, and on nonionic polymers in nonadsorbing solutions. In the final section of the book, the interactions of macromolecules with complex colloidal particles such as micelles, liposomes, and proteins are considered. 

Distribution of retained polymer in sandpacks showed an exponential function of the distance. The dynamic polymer retention values in short packs showed higher values than the static polymer adsorption values due to mechanical entrapment. 

This book presents coverage of the dynamics, preparation, application and physico-chemical properties of polymer solutions and colloids. It also covers the adsorption characteristics at and the adhesion properties of polymer surfaces. It is written by 23 contemporary experts within their field. Main headings include Structural ordering in polymer solutions Influence of surface Structure on polymer surface behaviour Advances in preparations and appUcations of polymeric microspheres Latex particle heterogeneity origins, detection, and consequences Electrokinetic behaviour of polymer colloids Interaction of polymer latices with other inorganic colloids Thermodynamic and kinetic aspects of bridging flocculation Metal complexation in polymer systems Adsorption of quaternary ammonium compounds art polymer surfaces Adsorption onto polytetrafluoroethylene from aqueous solutions Adsorption from polymer mixtures at the interface with solids Polymer adsorption at oxide surface Preparation of oxide-coated cellulose fibre The evaluation of acid-base properties of polymer surfaces by wettability measurements. Each chapter is well referenced. 

FIGURE 11.9 Schematic curve for the friction of a gel that is adhesive to the substrate in liquid. The friction is the sum of elastic force due to polymer adsorption and viscous force due to hydration of the polymer. At v Vf, the first component is dominant. At v Vf, the second component is dominant. Transition from elastic friction to lubrication occurs at the sliding velocity characterized by the polymer chain dynamics Vf = = T/ri/Jp. (Reprodnced from... 

In this chapter, some of the basic ideas on polymer adsorption at a solid-liquid interface are briefly discussed. The different types of polymer retention mechanism within a porous medium as referred to above are then reviewed, together with discussion of how these may be measured in the laboratory both static and dynamic adsorption are discussed in this context. Retention of HPAM and xanthan are then considered and the levels observed and their sensitivities to polymer, solution and porous medium properties are discussed. The effect of polymer retention in reducing core permeability is also considered. Finally, some work on the effect of polymer adsorption on two-phase relative permeability, which is of some relevance in the polymer treatment of producer wells in order to control water production, is reviewed. 

The general phenomenon of polymer adsorption/retention is discussed in some detail in Chapter 5. In that chapter, the various mechanisms of polymer retention in porous media were reviewed, including surface adsorption, retention/trapping mechanisms and hydrodynamic retention. This section is more concerned with the inclusion of the appropriate mathematical terms in the transport equation and their effects on dynamic displacement effluent profiles, rather than the details of the basic adsorption/retention mechanisms. However, important considerations such as whether the retention is reversible or irreversible, whether the adsorption isotherm is linear or non-linear and whether the process is taken to be at equilibrium or not are of more concern here. These considerations dictate how the transport equations are solved (either analytically or numerically) and how they should be applied to given experimental effluent profile data. 

Johnson H S, Douglas and Granick S (1993) Topological influences on polymer adsorption and desorption dynamics, Phys Rev Lett 70 3267-3270. 

For systems in which the polymer and filler have an affinity for each other [strong adsorption], increases in the surface area/ volume ratio of the filler can result in large changes in the volume fraction of polymer that is henceforth considered to be "bound" to the filler interface. Many changes in physical phenomena related to the polymer chain dynamics, e.g., the glass transition temperature [Tg] and degrees and rates of polymer crystallization, could be drastically altered due to this bound layer. This has been referred to as the "nano-effect." ° In cases where Tg shifts are observed, the effect is somewhat similar to that reported for thin polymer films. The most important result of an increased bound-polymer layer is the consequent changes in mechanical properties of the final composite.i ... 

In principle, dynamic aspects of polymer adsorption can be determined with the same methods as one uses to characterize static properties of the adsorbed polymer layer. Fleer et al. [1] have presented an overview of experimental methods for the determination of adsorption isotherms, the adsorbed layer thickness, the bound fraction, and the volume fraction profile. However, in order to determine the dynamics of some property of the adsorbed polymer layer, the characteristic time of the experimental method should be shorter than that of the process investigated. Moreover, flie geometry of the experimental system is often of crucial importance. These factors severely limit the applicability of some experimental methods. In this section we will particularly review those methods which have been successfully applied for characterizing the kinetics of polymer adsorption. 

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