Flory-Huggins chi parameter

Polymer interfaces are usually much broader than inorganic interfaces because, even in the case of immiscible polymers, some segment interpenetration occurs at the interface between the individual domains, being the interfacial width (iv) proportional to where x is the Flory-Huggins chi-parameter [13]. Therefore,... 

Polymer simulations can be mapped onto the Flory-Huggins lattice model. For this purpose, DPD can be considered an off-lattice version of the Flory-Huggins simulation. It uses a Flory-Huggins % (chi) parameter. The best way to obtain % is from vapor pressure data. Molecular modeling can be used to determine %, but it is less reliable. In order to nm a simulation, a bead size for each bead type and a % parameter for each pair of beads must be known. 

The tendency of differing blocks to microseparate from each other is quantified by Flory s chi parameter /, introduced in Chapter 2. An increasing, positive value of x implies an increasing tendency for the two chemically dissimilar species to segregate from each other. As discussed in Section 2.3.1.2, for a blend of two different homopolymers (A and B) of equal degree of polymerization Na — Ag at a 50/50 composition, the Flory-Huggins theory predicts that phase separation should occur at a critical value of Xc = For block... 

The parameter xi is a measure of the interaction enthalpy per solvent molecule. It is called the Flory-Huggins interaction parameter, or simply interaction parameter, or sometimes chi parameter. Since the second virial coefficient is given by... 

For the Flory-Huggins model of the activity, Equations (2C-4)-(2C-6), the data are reported in terms of a concentration dependent chi parameter. Data must be taken or extrapolated to the 6 = 0 limit in order to remove solution structure effects. 

This example shows how to calculate a weight fraction activity coefficient from the Flory-Huggins method when the chi parameter is known. 

As the volume of tabulated values of thermodynamic parameters indicates, the largest pool of data is based on Flory-Huggins type of relations. This is only to be expected since the theory, and the related concept of the binary interaction parameters, either B or X 2, was introduced to polymer science very early, more than a half century ago, in 1941 to be precise. Even with its rather limited applicability, due to its strict assumptions, and the well-recognized complexity of functional dependence [viz., % = chi T, P, (f>, M, MWD, molecular... 

Based on lattice model simulations (for N typically in the range 16-256). Binder and co-workers have discovered a host of non-mean-field, or fluctuation, phenomena in the symmetric blend model, most of which appear to be nonuniversal. In particular, in contrast to Flory-Huggins theory, an effective, or renormalized, chi parameter that deviates from the mean-field behavior [see Eq. (5.2)] in many ways was observed ... 

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