Viscosity polymer-surfactant

Recent investigations have shown that the behavior and interactions of surfactants in a polyvinyl acetate latex are quite different and complex compared to that in a polystyrene latex (1, 2). Surfactant adsorption at the fairly polar vinyl acetate latex surface is generally weak (3,4) and at times shows a complex adsorption isotherm (2). Earlier work (5,6) has also shown that anionic surfactants adsorb on polyvinyl acetate, then slowly penetrate into the particle leading to the formation of a poly-electroyte type solubilized polymer-surfactant complex. Such a solubilization process is generally accompanied by an increase in viscosity. The first objective of this work is to better under-stand the effects of type and structure of surfactants on the solubilization phenomena in vinyl acetate and vinyl acetate-butyl acrylate copolymer latexes. 

J = 1 1 1 1 1 1 1 - 4> 0.97 0.95 L A r no rigure viscosity as a lunc-tion of shear stress for an aqueous polymer-surfactant foam at the bubble volume fractions 0 shown. (From Khan et al. 1988, with permission... 

Electron spin resonance spectroscopy (ESR), also known as electron paramagnetic resonance (EPR), is based on the property that an unpaired electron placed in a magnetic field shows a typical resonance energy absorption spectrum sensitive to its environment. Recently, this technique, which was primarily developed for biological studies of membrane properties, has been adapted for the study of adsorbed polymer/surfactant layers. The mobility of the ESR probe (stable free radical incorporated into the polymer or surfactant molecule) depends of orientation of the surfactant or polymer and the viscosity of the local environment around the probe. 

These results were obtained in experiments with biliquid foam (emulsions such as oil in water ) and polymer surfactants for drop diameters 8.3 x 10-6 to 26.3 x 10"6 m and for the disperse phase viscosity 2.65 x 10-3 to 6.6 x 10" Pa s. 

There is a lack of systematic experimental studies. Only on the basis of a large data base can further improvements in the theories be made. Thus, the more effective instruments and newly developed techniques should enable surface scientists to produce more systematic data. There is also a deficiency in respect to relaxation theories for polymers and mixed polymer/surfactant systems. First ideas about dilational properties of composite adsorption layers were published by Lucassen (1992). A theory has also been developed by Johnson Stebe (1994) to differentiate exchange of matter from dilational viscosity. This calls for new experimental developments. 

The solubilization of the HMHEC in the surfactant was attributed to the interactions between surfactant micelles and polymer-bound hydrophobes. The effect of pH on polymer-surfactant solution viscosity was explained in terms of charge effects at the surface of the surfactant micelles. Steiner (13) proposed that at pH levels above or below the isoelectric point, the surfactant has a net charge on the head groups that causes repulsion within a single micelle. This repulsion leads to a relatively open micelle-aqueous phase interface through which polymer-bound hydrophobes can enter and experience stable polymer-surfactant interactions. These interactions anchor the polymer chains in an extended configuration. 

The effect of different counterions on the viscosity stability of HMHEC-surfactant at pH 7 was also studied at 10% and 20% surfactant concentrations (Tables I and II). The most stable solutions were formed in the presence of fumaric and mellitic (benzenehexacarboxylic) acid. By contrast, citric and maleic acid occasioned relatively higher viscosity loss. These results indicate that the viscosity stability of a polymer-surfactant solution is dependent on the counterion configuration. It appears that flexible and difunctional anions, such as citrate, and cis-difunctional anions such as ma-leate ions can potentially bridge two surfactant head groups on a single... 

Polymer-surfactant interactions are the basis for the rheological behavior of MHAPs. Other surfactant-polymer systems have previously been investigated. One example is the interaction of surfactants with polymers such as poly(ethylene oxide), which results in greater solution viscosities than with the polymer alone (e.g., ref. 25 and references therein). The interaction of surfactants or latexes with hydrophobically modified water-soluble polymers has also been shown to produce unique rheology (2, 5, 26, 27). In these systems, the latex particles or the surfactant micelles serve as reversible cross-link points with a hydrophobic region of a polymer molecule in dynamic association with a latex particle or surfactant micelle (27). 

One such method involves the use of water-soluble polymers such as polyacrylamide to increase the relative viscosity of sweep water to that of the crude oil so as to promote the mobility of the residual oil in the reservoir. Polyacrylamide, although relatively cheap, does not possess the useful properties of polysaccharides such as xanthan gums, scleroglucan, dextran, etc. The biopolymers are injected at a rate of 1.4 to 1.7 lb arrel of oil recovered. Excluding the polymer, the cost of the polymer/surfactant flood amounts to 30 nd 40 arrel, including capital charges. 

The peak in the plot of viscosity vs. surfactant concentration in general occurs in the vicinity of the CAC. Here, the composition of the mixed HM-polymer-surfactant micelles changes strongly with concentration to become dominated by the surfactant thus, the cross-linking effect is lost. 

Experimental methods for investigating polymer-surfactant interactions vary widely, but they generally fall into two categories those that measure the macroscopic properties of a system (viscosity, conductivity, dye solubilization, etc.) and those that detect changes in the molecular environment of the inter-... 

The principal goal of this paper is to examine the physical forces responsible for this latter type of polymer-surfactant micelle association. Since the formation of a polymer-micelle complex gives rise to gross conformational changes in the polymer molecule, a measurement of the solution viscosity provides the simplest means for monitoring polymer-micelle association. Here, the viscosity data on solutions containing polymer and surfactant of different molecular structures are used to explore the nature of polymer-miceUe complex formation. 

The viscosities of polymer-surfactant solutions as well as those of the surfactant and of the polymer alone have been measured at 25 using a Cannon-Fenske capillary viscometer. Two high molecular weight nonionic polymers and anionic, cationic and nonionic surfactants have been used in this study (Table I). 

Viscosity is one of the most frequently applied method to study the polymer surfactant interaction. The hydrodynamic data are expressed in various ways viscosities relative to the solvent (water) or to the surfactant solution furthermore, specific viscosity measured as a function of polymer concentration at constant surfactant concentration and as a function of surfactant concentration at constant polymer content as well as measurements at a constant polymer/surfactant concentration ratio can be found in the literature. In some cases, efforts were made in order to determine the intrinsic viscosity of the polymer-surfactant complex by extrapolation from the linear region of the Tigp/cp vs. Cp function in spite of the fact that at low polymer concentration it shows anomaly. ... 

The intrinsic viscosity of the complex can be determined by dilution of the system neither at constant polymer/surfactant concentration ratio nor at constant surfactant concentration, because the composition of the complex (the number of surfactant ions in one polymer coil) and the ionic strength of the solution are to be kept constant under dilution. Therefore, the dilution of the polymer-surfactant solution was performed by using as a diluent the surfactant solution being in dialysis equilibrium with the PVA-NaDS complex. The equilibrium surfactant concentration was found to be independent of the amount of the complex in the system, so the dilution was carried out at constant ionic strength as well. 

Hence there is no possibility to get even a qualitative conclusion about the role of the different parameters which determine the behavior of the polymer-surfactant complex as a whole. It is concluded, however, that the viscosity measurements are not suitable to compare the strength of complexes, or, in some cases, not even to indicate the interaction itself. The polymer-ionic surfactant complex seems to be a unique model to study the behavior of polyelectrolytes in which the charges are not individually distributed over the chain. 

Low Tension Polymer Water Flood. In oil reservoirs, where the critical capillary number is relatively low, a significant amount of waterflooded residual oil can be displaced by surfactants of high efficiency even at two-phase flood conditions. This was demonstrated by the snccessfnl second Ripley surfactant flood pilot test in the Loudon field where approximately 68% of waterflooded residual oil was recovered by injecting a 0.3 PV microemulsion bank [63]. The microemulsion bank was followed by I.O PV of higher viscosity polymer drive. The chemical formnlation consisted of a blend of two PO-EO sulfates. 

To describe the observed nonmonotonic behavior of the mechanical modulus and viscosity of the polymer-surfactant mixtures, we introduce a mini-max model of the junctions (7.127), for which... 

Actually, the viscosity method can be considered a traditional method to study polymer/surfactant interaction and its first use was by Saito, who reported increases in viscosity of PVP and MeC solutions on adding SDS (31). Its subsequent popularity is, undoubtedly, connected with the simple nature of the equipment that can be used for its measurement. 

Viscosity increases and gel formation in polyanion-cationic surfactant systems have also been reported, for example by Thalberg and Lindman (86) for hyaluronan and polyacrylate polymers in combination with alkyltrimethylammononium bromide surfactants. Similarly, viscosity increases and gel formation with polymers such as carboxymethyl cellulose (CMC) and CTAB at relatively low polymer-surfactant levels have been observed (87). 

Interaction of nonionic surfactants with most polymers is relatively weak and therefore signiflcant increases in viscosity resulting from polymer-surfactant interactions do not occur unless the polymer has been suitably hydrophically modified (see below). However, interaction of the EO groups of nonionic surfactants with polyacrylic acid-based polymers and copolymers is known and this can lead to substantial alterations in viscosity (91,92). This behavior is associated with the specific interaction of polyethers and polycarboxylic acids (92). 

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