Solubilization polymer-surfactant interaction

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. 

This book on polymeric microemulsions is an attempt at a rapprochement of the methods and structures encountered in the two disciplines. The purpose of this book is to investigate polymer-polymer or polymer-surfactant interactions in solution leading to association structures with properties such as solubilization and anisotropy. These properties are useful in a wide variety of industries such as pharmaceutics, cosmetics, textiles, detergents, and paints. 

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. 

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-... 

Nizri G, Magdassi S (2005) Solubilization of hydrophobic molecules in nanoparticles formed by polymer-surfactant interactions. J Colloid Interface Sci 291 169... 

The ability of surfactants to form complexes with polymer chains may also affect the ultimate properties and stability of the resulting polymer, especially when the macromolecule exhibits some affinity for or reactivity with water. Perhaps the best documented case of the effect of surfactant on latex stability is that of polyvinyl acetate. The stability of PVAc latexes has been found to vary significantly depending on the surfactant employed in its preparation. It has also been found that PVAc could be dissolved in concentrated aqueous solutions of SDS and that it did not precipitate on dilution. The results suggest that, in this case at least, solubilization did not occur in the micelle, but that extensive adsorption of surfactant onto the polymer chain was required. They also indicate that a strong, stable PVAc-SDS complex is formed that produces a water-soluble structure that is essentially irreversible, imlike normal micelle formation. Cationic and nonionic surfactants had little or no solubilizing effect under identical conditions, indicating the specific nature of many, if not most, polymer-surfactant interactions. 

Intermixing of the polymer mobility control fluid with the surfactant slug can result in surfactant - polymer interactions which have a significant effect on oil recovery (476). Of course, oil - surfactant interactions have a major effect on interfacial behavior and oil displacement efficiency. The effect of petroleum composition on oil solubilization by surfactants has been the subject of extensive study (477). 

Polymers Interact with surfactants and mlcroemulslons In diverse. Interesting and technologically Important wavs(1.21. The mechanisms that are responsible for the Interactions Include the usual panoply of forces Involved In the interaction of any two different molecules lon-lon, lon-dlpole, dlpole-dlpole, and van der Waals forces all modulated by the presence of solvent and/ or other species such as dissolved salts. All may play a role. The special factors Involved in surfactant/polymer and polymer-/mlcroemulslon Interactions that form the basis for their particular interest lies in their tendencies to form a variety of supermolecular clusters and conformations, which In tuim may lead to the existence of separate phases of coexisting species. Micelles may form In association with the polymer, polymer may precipitate or be solubilized, mlcroemulslon phase boundaries may change, and so on. 

In summary, NMR studies can deal with a wide range of problems in surfactant science. These include, e.g., molecular transport, phase diagrams, phase structure, self-association, micelle size and shape, counterion binding and hydration, solubilization, and polymer-micelle interactions. NMR is fruitfully applied to isotropic or liquid crystalline bulk phases, to dispersions (vesicles, emulsions, etc.), to polymer-surfactant mixtures, and to surfactant molecules at solid surfaces. In all cases NMR can provide information on molecular interactions and dynamics as well as on microstructure. 

It has been suggested that cuticular wax can be solubilized by surfactant micelles (by the same mechanism of solubilization of the agrochemical). However, no evidence could be presented (for example using SEM) to show the wax disruption by the micelles. Schonherr [126] suggested that the surfactants interact with the waxes of the cuticle and thus increase the fluidity of this barrier. This hypothesis is sometimes referred to as wax Plasticization (similar to the phenomenon of the glass transition temperature reduction of polymers by addition of plasticizers). Some measurements of uptake using surfactants with various molecular weights and HLB numbers offered some support for this hypothesis. 

Studies on the interaction between surfactants and styrene-ethylene oxide block co-polymers, however, indicate that the polymers exhibit, in the presence of surfactant, typical polyelectrolyte character. This, it has been suggested [264], is due to interaction repulsions between like charges of the NaDS ions adsorbed onto the polyoxyethylene blocks. Investigating the interaction of the same detergent with methylcellulose and poly(vinyl alcohol), Lewis and Robinson [265] also observed the polyelectrolyte character of the polymer-surfactant complexes. A complex between non-ionic surfactants and a polycarboxylic acid in water can solubilize oil-soluble dyes below the surfactant CMC [268]. The complex containing the solubilizate can be precipitated the solubilizate remains in the precipitated complex and is leached out only slowly on placing the precipitate in fresh solvent. This has potential pharmaceutical implications. Halothane uptake by coacervate systems of gelatin-benzalkonium [269] has... 

The solubilization of hydrosoluble polymers, like poly ethyleneglycol (PEG), in the water pools of reverse micelles is known to produce a decrease of the interdroplet attractive interactions, at least when the polymer chains are smaller than the water droplets. Addition of PEG (molecular weight 2000 or 10,000 at maximum) to water/AOT/n-decane systems shifts the threshold of conductivity percolation to higher water volume fractions, as expected, because of the polymer/surfactant stabilizing interactions. Similar observations were reported for water/AOT/isooctane reverse micelles in the presence of triblock copolymers or of PEG of varied molecular weights. ... 

Interactions between polymers and surfactants have been widely investigated in the recent decades. The interaction may lead to a polymer-surfactant complex formation, which may have a significant influence on the system properties e.g. emulsification, colloidal stability, viscosity enhancement, gel formation, solubilization, and phase separation [Goddard 1993a Goddard 2002]. The properties and structure of surfactant-polymer complexes depend on the molecular characteristics of both the polymer and surfactant [Lindman Thalberg,... 

It is well known (3,5,6) that sodium lauryl sulfate interacts with some polymers such as polyvinyl acetate causing solubilization of the insoluble polymer leading to an increase in viscosity. In Figure 3, viscosity of the homopolymer and 70/30 VA/BA at various NaLS/polymer ratio is shown. It is seen that the viscosity of the 2% latex dispersion increases with increase in NaLS/polymer ratio. Similar visoosity data for the 85/15 VA/BA was intermediate between the homopolymer and 70/30 VA/BA latexes. Surfactants that showed a normal saturation type adsorption behavior did not show any significant visoosity increase of the latex. 

In this paper, the results on solution and Interfaclal properties of a cationic celluloslcs polymer with hydrophobic groups are presented. Interaction of such polymers with added surfactants can be even more complex than that of "unmodified" polymers. In the past we have reported the results of Interactions of unmodified cationic polymer with various surfactants Investigated using such techniques as surface tension, preclpltatlon-redlssolutlon, viscosity, solubilization, fluorescence, electroklnetlc measurements, SANS,etc.(15-17). Briefly, these results showed that as the concentration of the surfactant Is Increased at constant polymer level significant binding of the surfactant to the polymer occurred leading to marked Increases In the surface activity and viscosity. These systems were able to solubilize water Insoluble materials at surfactant concentrations well below the CMC of polymer-free surfactant solutions. Excess surfactant beyond that required to form stoichiometric complex was found to solubilize this Insoluble complex and Information on the structure of these solubilized systems has been presented. 

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