Effects of polydispersivity on the phase behavior of the aqueous two-phase polymer systems

Single‐stage fractionation of poly(ethylene‐co‐vinyl acetate) in supercritical ethylene with saft

“…The SAFT predictions of the extract and the raffinate polydispersity for the same dew-point-type fractionation are shown in Figure 16. Similarly to what was observed for the bubble-point-type fractionation (Figure 14), the polymer polydispersity in both phases is less than that of the parent EVA, as reported elsewhere (Kang and Sandler, 1988;Kang et al, 1989;Spahl and Luft, 1983). Those simulation results also indicate that under identical operating conditions a dew-point-type fractionation is more efficient than a bubblepoint-type fractionation to raise the raffinate M,, and to reduce its polydispersity.…”

“…By cumulating probabilities (p,), we obtain the cumulative weight probability distribution from which the weight fraction of the ith pseudocomponent is easily obtained from where the cumulative weight probabilities (Cwis) are estimated by interpolating between the data points with cubic splines. It should be pointed out that an elegant method, the so-called generalized Gaussian quadrature method, developed by Cotterman and Prausnitz (1985) and used elsewhere (Kang and Sandler, 1988;Kang et al, 1989), exists for estimating the pseudocomponents in a mathematically correct and optimal way, given a continuous distribution function for Two sets of criteria are used to determine the optimum number of pseudocomponents. First, the reconstructed EVA M,,, and M,, are calculated according to Mi.…”

The influence of thermodynamic activity on the solute rejection in multicomponent systems

“…The model presented here is a simplified model which does not take the molecular weight distribution of the polymers into account. (For the extended model with molecular weight distribution, see Kang and Sandler [35].) First, a general description of the model is given.…”

Modeling of phase separation in PEG–salt aqueous two‐phase systems

“…Brooks and coworkers (1985) used the Flory-Huggins theory to develop a lattice model that gives a qualitative description of the phase separation observed in a mixture of polymer solutes. Sandler (1987, 1988,) combined the Flory-Huggins theory and the UNIQUAC model of Abrams and Prausnitz (1975) to develop models of PEG-dextran aqueous two-phase systems that take into account the effects of polydispersivity (Kang and Sandler, 1988b) and temperature (Hartounian et al, 1993). Hsu (1989, 1990) modified the Flory-Huggins theory for polymer solutions to obtain a semiempirical expression for protein partitioning in PEG-dextran aqueous two-phase systems both in the presence and absence of salts.…”