Interaction energy density, polymer blends

When the interaction energy density is positive, equation 5 defines a critical temperature of the UCST type (Fig. la) that is a function of component molecular weights. The LCST-type phase diagram, quite common for polymer blends, is not predicted by this simple theory unless B is... 

The interaction parameter X12 is dimensionless, and its numerical value depends on the choice of the lattice volume V f. In the case of polymer solutions, is usually equated to the volume of a solvent molecule and no ambiguity arises, but in the case of polymer blends, the practice of implicitly equating to the volume of a monomer unit is not satisfactory since the monomer volumes of polymers 1 and 2 are usually significantly different from each other. For experimental evaluation the interaction energy density Ajj, given in terms of a specific unit such as joules/cm, avoids such ambiguity. 

Table 10.1 Flory Interaction Parameter, Xab, and Interaction Energy Density, B, for Miscible Binary Blends of Varions Polymers...

By using experimental values of the binary interaction parameters it is possible to calculate miscibility maps and therefore predict the phase behavior of polymer/copolymer, copolymer/copolymer, and more complex blends. A list of segment-segment interaction parameters and corresponding interaction energy densities, By, where... 

Lohse et al. have summarized the results of recent work in this area [21]. The focus of the work is obtaining the interaction parameter x of the Hory-Huggins-Stavermann equation for the free energy of mixing per unit volume for a polymer blend. For two polymers to be miscible, the interaction parameter has to be very small, of the order of 0.01. The interaction density coefficient X = ( y/y)R7 , a more relevant term, is directly measured by SANS using random phase approximation study. It may be related to the square of the Hildebrand solubility parameter (d) difference which is an established criterion for polymer-polymer miscibility ... 

As discussed above, the solubility parameter is usually assumed to be equal to the square root of the cohesive energy density. It thus encompasses all of the different types of forces of cohesion in a material. Sometimes, however, the solvation of a polymer by a solvent, the behavior of plasticizers, pigments and other additives, or the blending of two polymers, requires certain specific types of interactions to exist between the polymer and the solvent, or between the two polymers that are to be blended. In such cases, the matching of the strengths of these specific types of interactions may play a crucial role in solvation or miscibility, and a more refined treatment may be necessary than can be provided by a single-valued solubility... 

Polymer interactions can be described in terms of temperature and composition-dependent raiCTgy density parameter, Bj2- For a blend of two statistical copolymCTs, A B, x and CyD, y, the blend interaction energy draisity is givrai by... 

Can we expect this to be the case here To estimate the range of the reweighting factor, we briefly re-inspect the Hubbard-Stratonovich transformation of the total density + < b that leads to the fluctuating field 17. For simplicity we consider a one-component system. In a compressible polymer solution or blend, the contribution of the repulsive interaction energy to the partition function can be written as... 

Ethylene-vinyl acetate copolymer, terpene-phenol resins, polyethylene oxide, PMMA and some of their blends were solution cast on basic (aluminium oxide) and acidic (hydroxylated glass) substrates. Fourier transform infrared reflection absorption spectroscopy (IRRAS) was used to determine both the nature and the free energy of interfacial adduct formation in the polymer/metal systems. A correlation between IRRAS and adhesive strength may be used to predict both the acid-base work of adhesion and the density of interfacial interacting sites. 14 refs. 

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