Parameters Influencing Miscibility

As can be seen from the above equation, X 2 and Q 2 are the parameters that control miscibility. In the absence of strong interactions such as hydrogen bonding, dipole-induced dipole or strong dipolar interactions, physical parameters or the equations of state parameters of the homopolymer become important. Clearly the equations of state parameters are also determined by polymer-polymer interactions but now the important factor is the relative balance between these interactions. Detailed theories have been produced which look in more detail at the effects of the various interactions.  

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The procedure chosen for the preparation of lipid complexes of AmB was nanoprecipitation. This procedure has been developed in our laboratory for a number of years and can be applied to the formulation of a number of different colloidal systems liposomes, microemulsions, polymeric nanoparticles (nanospheres and nanocapsules), complexes, and pure drug particles (14-16). Briefly, the substances of interest are dissolved in a solvent A and this solution is poured into a nonsolvent B of the substance that is miscible with the solvent A. As the solvent diffuses, the dissolved material is stranded as small particles, typically 100 to 400 nm in diameter. The solvent is usually an alcohol, acetone, or tetrahydrofuran and the nonsolvent A is usually water or aqueous buffer, with or without a hydrophilic surfactant to improve colloid stability after formation. Solvent A can be removed by evaporation under vacuum, which can also be used to concentrate the suspension. The concentration of the substance of interest in the organic solvent and the proportions of the two solvents are the main parameters influencing the final size of the particles. For liposomes, this method is similar to the ethanol injection technique proposed by Batzii and Korn in 1973 (17), which is however limited to 40 mM of lipids in ethanol and 10% of ethanol in final aqueous suspension. 

The action of phospholipase A2 on mixed monolayers of natural and polymerizable lipids can be measured under constant surface pressure by the contraction of the monolayer as a function of time as depicted schematically in Fig. 39. It turns out that the chief parameter influencing the enzymatic activity is the miscibility of the lipid components and not the fact whether the film is polymerized or not. In mixed and demixed membranes the enzyme is able to hydrolyze the natural lipid component, but with considerable differences in the hydrolizing rate (Fig. 40). A pure dilauroyllecithin (DLPC) monolayer is completely hydrolyzed in a few minutes after injecting the enzyme... 

Bues, M.A., and M. Aachib. 1991. Influence of the heterogeneity of the solutions on the parameters of miscible displacement in saturated porous medium. I. Stable displacement with density and viscosity contrasts. Exp. Fluids 11 25-32. 

First experiments investigating the action of phospholipase A2 on mixed membrane systems have been carried out in monolayers measuring the area contraction under constant surface pressure vs. time. As can be seen in fig. 15. the main parameter influencing enzyme activity is the miscibility... 

In real systems, nonrandom mixing effects, potentially caused by local polymer architecture and interchain forces, can have profound consequences on how intermolecular attractive potentials influence miscibility. Such nonideal effects can lead to large corrections, of both excess entropic and enthalpic origin, to the mean-field Flory-Huggins theory. As discussed in Section IV, for flexible chain blends of prime experimental interest the excess entropic contribution seems very small. Thus, attractive interactions, or enthalpy of mixing effects, are expected to often play a dominant role in determining blend miscibility. In this section we examine these enthalpic effects within the context of thermodynamic pertubation theory for atomistic, semiflexible, and Gaussian thread models. In addition, the validity of a Hildebrand-like molecular solubility parameter approach based on pure component properties is examined. 

The slopes of the peaks in the dynamic adsorption experiment is influenced by dispersion. The 1% acidified brine and the surfactant (dissolved in that brine) are miscible. Use of a core sample that is much longer than its diameter is intended to minimize the relative length of the transition zone produced by dispersion because excessive dispersion would make it more difficult to measure peak parameters accurately. Also, the underlying assumption of a simple theory is that adsorption occurs instantly on contact with the rock. The fraction that is classified as "permanent" in the above calculation depends on the flow rate of the experiment. It is the fraction that is not desorbed in the time available. The rest of the adsorption occurs reversibly and equilibrium is effectively maintained with the surfactant in the solution which is in contact with the pore walls. The inlet flow rate is the same as the outlet rate, since the brine and the surfactant are incompressible. Therefore, it can be clearly seen that the dynamic adsorption depends on the concentration, the flow rate, and the rock. The two parameters... 

For epoxy networks modified by liquid reactive rubbers, it is not so easy to discuss these parameters separately, because they are interdependent. For example, an increase in the acrylonitrile content of the carboxy-termi-nated butadiene acrylonitrile rubber (CTBN) induces a size reduction of the rubbery domains but also a higher miscibility with the epoxy-rich phase, leading to a higher amount remaining dissolved in the matrix at the end of cure (Chapter 8). It is not possible to separate the influence of these two effects on toughness. 

Attempts have been made to correlate the influence of solvents on enzyme activity, stability, and selectivity with physicochemical solvent characteristics such as relative permittivity, dipole moment, water miscibility, and hydrophobicity, as well as empirieal parameters of solvent polarity. However, no rationale of general validity has been found, except the simple rule that nonpolar hydrophobic solvents are generally better than polar hydrophilic ones. The best correlations are often obtained with the logarithm of the 1-octanol/water partition coefficient, Ig Pq/wj a quantitative measure of the solvent s hydrophobicity cf. Section 7.2). 

The varieties of copolymers that can be prepared with styrene have greatly expanded the use of the monomer. Dramatic improvements or modifications of physical properties can be achieved by choosing the right comonomer. The dynamic mechanical properties of these copolymers are strongly influenced by the characteristics of the comonomer, the copolymer composition and the miscibility parameter of the constituents parts to function as separable identities. 

Diffusion rates are high and viscosity is low in a supercritical aqueous mixture. Transport properties and miscibility are important parameters, which influence the rate of chemical reactions. High diffusion rates and low viscosity, together with the complete miscibility with many substances, make supercritical water an excellent medium for homogeneous, fast, and efficient reactions. In addition, SCW is an excellent reaction medium with heterogeneous catalysts, because the high diffusion rate avoids mass transfer limitations and efficient solubility prevents coke formation on, or poisoning of the catalyst. 

Two types of rheological phenomena can be used for the detection of blend s miscibility (1) influence of polydispersity on the rheological functions, and (2) the inherent nature of the two-phase flow. The first type draws conclusions about miscibility from, e.g., coordinates of the relaxation spectmm maximum cross-point coordinates (G, CO ) [Zeichner and Patel, 1981] free volume gradient of viscosity a = d(lnT]) / df the initial slope of the stress growth function S = d(lnr +g)/dlnt the power-law exponent n = d(lnOj2)/dlny = S, etc. The second type involves evaluation of the extrudate swell parameter, B = D/D, strain (or form) recovery, apparent yield stress, etc. 

Abstract We put together the state of knowledge on binary colUsional interactions of droplets in a gaseous environment. Phenomena observed experimentally after drop collisions, such as coalescence, bouncing, reflexive separation and stretching separation, are discussed. Collisions of drops of the same liquid and of different -miscible or immiscible - liquids, as well as collisions of drops of equal and different size are addressed. Collisions of drops of immiscible liquids may lead to an unstable interaction which is not observed with drops of equal or miscible liquids. Regimes characterized by the various phenomena are depicted in nomograms of the Weber number and the non-dimensional impact parameter. The state-of-the-art in the simulation of binary droplet collisions is reviewed. Overall three different methods are represented in the literature on these simulations. We discuss models derived from numerical simulations and from experiments, which are presently in use for simulations of spray flows to account for the influence of coUisional interactions of the spray droplets on the drop size spectrum of the spray. 

The impact of inaccurate -model parameters can be very serious. The parameters have a major influence on the investment and operating costs (number of stages, reflux ratio), The influence of the -model parameters on the results is especially large if the separation factor is close to unity. Poor parameters can either lead to the calculation of nonexisting azeotrojjes in zeotropic systems (see Section 11.1) or the calculation of zeotropic behavior in azeotropic systems. Poor parameters can also lead to a miscibility gap which does not exist." In the case of positive deviation from Raoult s law a separation problem often occurs at the top of the column, where the high boiler has to be removed, since at the top of a distillation column the most unfortunate separation factors are obtained. 

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