Interfacial tension polymer effects

The method, however, fails to retain viscous, low interfacial tension polymer phase systems such as polyethylene glycol (PEG)-dextran systems due to its intensive mixing effect which tends to produce emulsification, resulting in carryover of the stationary phase. This problem is largely eliminated by the crossaxis CPC described below. 

Elias, L., Fenouillot, F., Majeste, J.C., Alcouffe, P., and Cassagnau, P. (2008) Immiscible polymer blends stabilized with nano-silica particles rheology and effective interfacial tension. Polymer, 49, 4378-4385. 

The theory of Leibler holds for mainly compatible systems. Leibler developed a mean field formalism to study the interfacial properties of two polymers, A and B with an A-B copolymer. An expression for interfacial tension reduction was developed by Noolandi and Hong [ 18] based on thermodynamics to explain the emulsifying effect of the A-b-B in immiscible A-B blends (A-A-b-B-B). [18,19]. The expression for interfacial tension reduction Ar) in a binary lend upon the addition of divalent copolymer is given by ... 

The rheological properties of a fluid interface may be characterized by four parameters surface shear viscosity and elasticity, and surface dilational viscosity and elasticity. When polymer monolayers are present at such interfaces, viscoelastic behavior has been observed (1,2), but theoretical progress has been slow. The adsorption of amphiphilic polymers at the interface in liquid emulsions stabilizes the particles mainly through osmotic pressure developed upon close approach. This has become known as steric stabilization (3,4.5). In this paper, the dynamic behavior of amphiphilic, hydrophobically modified hydroxyethyl celluloses (HM-HEC), was studied. In previous studies HM-HEC s were found to greatly reduce liquid/liquid interfacial tensions even at very low polymer concentrations, and were extremely effective emulsifiers for organic liquids in water (6). 

Divisek et al. presented a similar two-phase, two-dimensional model of DMFC. Two-phase flow and capillary effects in backing layers were considered using a quantitatively different but qualitatively similar function of capillary pressure vs liquid saturation. In practice, this capillary pressure function must be experimentally obtained for realistic DMFC backing materials in a methanol solution. Note that methanol in the anode solution significantly alters the interfacial tension characteristics. In addition, Divisek et al. developed detailed, multistep reaction models for both ORR and methanol oxidation as well as used the Stefan—Maxwell formulation for gas diffusion. Murgia et al. described a one-dimensional, two-phase, multicomponent steady-state model based on phenomenological transport equations for the catalyst layer, diffusion layer, and polymer membrane for a liquid-feed DMFC. 

The integrated DLS device provides an example of a measurement tool tailored to nano-scale structure determination in fluids, e.g., polymers induced to form specific assemblies in selective solvents. There is, however, a critical need to understand the behavior of polymers and other interfacial modifiers at the interface of immiscible fluids, such as surfactants in oil-water mixtures. Typical measurement methods used to determine the interfacial tension in such mixtures tend to be time-consuming and had been described as a major barrier to systematic surveys of variable space in libraries of interfacial modifiers. Critical information relating to the behavior of such mixtures, for example, in the effective removal of soil from clothing, would be available simply by measuring interfacial tension (ILT ) for immiscible solutions with different droplet sizes, a variable not accessible by drop-volume or pendant drop techniques [107]. 

The properties of immiscible polymers blends are strongly dependent on the morphology of the blend, with optimal mechanical properties only being obtained at a critical particle size for the dispersed phase. As the size of the dispersed phase is directly proportional to the interfacial tension between the components of the blend, there is much interest in interfacial tension modification. Copolymers, either preformed or formed in situ, can localize at the interface and effectively modify the interfacial tension of polymer blends. The incorporation of PDMS phases is desirable as a method to improve properties such as impact resistance, toughness, tensile strength, elongation at break, thermal stability and lubrication. 

The end groups of a PDMS polymer have been shown to affect the interfacial tension of blends with poly(butadiene)126. Thus, substitution of an amine-terminated PDMS for a trimethylsilyl-terminated PDMS can reduce the interfacial tension by up to 30%. This effect is postulated to arise due to the amine end group having a surface energy closer to that of butadiene than does the trimethylsilyl group and thus being present at the interface. 

Fleischer CA et al. (1993) The effect of end groups on thermodynamics of immiscible polymer blends. 1. Interfacial tension. Macromolecules 26(16) 4172-4178... 

Wagner M, Wolf BA (1993) Effect of block copolymers on the interfacial tension between two immiscible homopolymers. Polymer 34 1460-1464... 

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