Surfactant polymer interface

Usually polymeric substances of appropriate chemical structure and morphology which promote the miscibility of incompatible materials. Block copolymers are especially useful surfactants at the polymer/polymer interface because the two blocks can be made up from molecules of the individual polymers to be mixed. Typical compatibilisers in polymer blends are LDPE-g-PS in PE/PS CPE in PE/PVC acrylic- -PE, -PP, -EPDM in polyolefin/PA and maleic-g-PE, -PP, -EPDM, -SEBS in polyolefin/polyesters. 

Attempts to correlate the adsorption data of other surfactants such as Alipal EP-110 and NaLS on the three latex surfaces in a similar manner failed because of the more complex and specific interactions observed in these systems. Equation 2 can adequately describe the adsorption data of surfactants at polymer/ water interfaces, provided that the free energy of the interface is related to the free energy of adsorption and there are no specific interactions between surfactant and interface (15). 

The surface forces technique measures the force between molecules (eg. surfactants, polymers) adsorbed on mica sheets. In the case of large molecules such as polymers, the measurement is most sensitive to the regions closest to the solution and provides little direct information about the region adjacent to the surface. As it is a measurement between macroscopic surfaces, it is unable to provide information on microscopic chemical differences at the interface. Infrared spectroscopy could provide additional information about the quantity of adsorbed material on the mica surface, the identity and orientation of the adsorbed species, and possibly the nature of the surface linkage. 

For the encapsulation of pigments by miniemulsification, two different approaches can be used. In both cases, the pigment/polymer interface as well as the polymer/water interface have to be carefully chemically adjusted in order to obtain encapsulation as a thermodynamically favored system. The design of the interfaces is mainly dictated by the use of two surfactant systems, which govern the interfacial tensions, as well as by employment of appropriate functional comonomers, initiators, or termination agents. The sum of all the interface energies has to be minimized. 

In the Current State of the Art we will review some of the recent SANS and reflectivity data from ISIS, which also serve to point to future directions and opportunities. Recent reflectivity measurements, on the adsorption of polymers and polymer/surfactant mixtures at interfaces, surface ordering in block copolymer systems, time dependent inter-diffusion at polymer-polymer interfaces, and the contribution of capillary waves to interfacial widths, will be described. The use of SANS to investigate the dynamic of trans-esterification of polyester blends, the deformation of copolymers with novel morphologies, and the use of diffraction techniques to determine the structure of polymeric electrolytes, will be presented. 

It was observed that the formulations consisting of ethoxylated sulfonates and petroleum sulfonates are relatively insensitive to divalent cations. The results show that a minimum in coalescence rate, interfacial tension, surfactant loss, apparent viscosity and a maximum in oil recovery are observed at the optimal salinity of the system. The flattening rate of an oil drop in a surfactant formulation increases strikingly in the presence of alcohol. It appears that the addition of alcohol promotes the mass transfer of surfactant from the aqueous phase to the interface. The addition of alcohol also promotes the coalescence of oil drops, presumably due to a decrease in the interfacial viscosity. Some novel concepts such as surfactant-polymer incompatibility, injection of an oil bank and demulsification to promote oil recovery have been discussed for surfactant flooding processes. 

Aderangi N., Wasan D.T., Coalescence of single drops at a liquid-liquid interface in the presence of surfactants/polymers. Chem. Eng. Commun. 132 (1995),... 

Fundamental investigation of the system at the molecular level. This requires investigations of the structure of the solid/liquid interface, namely the structure of the electrical double layer (for charge-stabiUsed suspensions), adsorption of surfactants, polymers and polyelectrolytes and conformation of the adsorbed layers (e.g., the adsorbed layer thickness). It is important to know how each of these parameters changes with the conditions, such as temperature, solvency of the medium for the adsorbed layers, and the effect of addition of electrolytes. 

The effect of the adsorbed surfactant-polymer complex on the rheology of the air-aqueous solution interface is easily detected by the talc particle test (Regis-mond, 1997). A small quantity of calcined talc powder is sprinkled on the surface of the aqueous solution in a 10-cm Petri dish. A gentle current of air is directed tangentially to the talc particles for 1-2 s and then removed. The observed movement is noted in the following categories fluid (F), viscous (V), gel (G) (= almost no flow), solid (S) (= no flow), and viscoelastic (VE) (= net movement, with some recovery upon removal of air current). 

The effect of interaction of sodium dodecyl sulfate with the polymer, polyvinylpyrrolidone, on the foaming of aqueous solutions of the former has been investigated by Folmer and Kronberg (2000). Depending upon the surfactant and polymer concentrations, the foaming can either be decreased or increased. Foaming increases when surface and/or bulk viscosities are increased by the surfactant-polymer concentration it decreases when surfactant-polymer interaction in the bulk phase causes desorption of them from the air-aqueous solution interface. 

This paper presents observations on the difference in behavior of emulsification processes which can occur during surfactant and caustic flooding in enhanced recovery of petroleum. Cinephotomicrographic observations on emulsion characteristics generated at the California crude oil-alkaline solution interface as well as in the Illinois crude oil-petroleum sulfonate system are reported. The interdroplet coalescence behavior of oil-water emulsion systems appear to be quite different in enhanced oil recovery processes employing various alkaline agents as opposed to surfactant/polymer systems. 

Surfactant-polymer interactions in an aqueous solution have been studied by many researchers [132], and the adsorption and surface-induced self-assembly of the surfactant at the solid-aqueous interface have been recently studied [133]. On the other hand, these subjects have been rarely studied for oil solutions. The surfactant-polymer interaction in oil and the surface-induced self-assembly of surfactants at the oil-solid interface are important for further research studies to enhance the polymerization at the interface of the liquid/solid in reversed micellar solutions. 

Polymers and surfactants are used together sometimes to obtain desirable effects. Polymer-surfactant interactions in solution and at the interfaces can change the interfacial properties of the solid directly or indirectly. It is shown that depending on the nature of the polymer and the surfactant, polymers can affect flotation of quartz by affecting the adsorption of the surfactant on it [7]. 

Piculell L, Lindman B. 1992. Phase separation in surfactant/polymer mixtures. Adv Colloid Interface Sci 41 149 153. 

A foam is a dispersion of a gas in a liquid or a solid. The formation of foam relies on the surface activity of the surfactants, polymers, proteins, and colloidal particles to stabilize the interface. Thus, the foamability increases with increasing surfactant concentration up to critical micelle concentration because above critical micelle concentration, the unimer concentration in the bulk r ains nearly constant. The structure and molecular architecture of the foam is known to influence foam-ability and its stability. The packing properties at the interface are not excellent for very hydrophilic or very hydrophobic drug. The surfactant promoting a small spontaneous curvature at interface is ideal for foams. Nonionic surfactants are the most commonly used one. The main advantage with foams is its site-specific delivery and multiple dosing of the drug. ... 

Understanding the adsorption and conformation of polymeric surfactants at interfaces is key to understanding how these molecules act as stabilizers for suspensions and emulsions. Most basic theories on polymer adsorption and conformation have been developed for the solid/liquid interface (9). The same concepts may be applied for the liquid/liquid interface, with some modifications whereby some part of the molecule may reside within the oil phase, rather than simply staying at the interface. Such modifications do not alter the basic concepts, particularly when one deals with the stabilization by these molecules. 

The interfacial behaviour of surfactant-polymer mixtures, utilized for example in the stabilization of suspensions, depends on a complex interplay between different pair interactions. Addition of a polymer can either remove surfactant from a surface or enhance its adsorption, and vice versa, depending on the relative stability of the polymer-surfactant complexes in solution and at the interface. 

They are widely used as surfactants particularly in emulsification and polyurethane foam stabilization. They orient at air/liquid and solid/liquid boundaries in a manner suitable for lubrication of polymer interfaces. 

A special class of block copolymers with blocks of very different polarity is known as amphiphilic (Figure 10.1). In general, the word amphiphile is used to describe molecules that stabilize the oil-water interface (e.g., surfactants). To a certain extent, amphiphilic block copolymers allow the generalization of amphi-philicity. This means that molecules can be designed that stabilize not only the oil-water interface but any interface between different materials with different cohesion energies or surface tensions (e.g., water-gas, oil-gas, polymer-metal, or polymer-polymer interfaces). This approach is straightforward, since the wide variability of the chemical structure of polymers allows fine and specific adjustment of both polymer parts to any particular stabilization problem. 

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