Flory-Huggins interaction parameter miscibility

The Flory-Huggins Interaction Parameter. These ideas, based on a study of polymer miscibility, have been appHed to plasticizers according to the foUowiag equation ia which is the molar volume of the plasticizer, obtaiaed from molar mass figures and density values at T, and represents the iateraction parameter (11). 

Since there had not been any measurements of thermal diffusion and Soret coefficients in polymer blends, the first task was the investigation of the Soret effect in the model polymer blend poly(dimethyl siloxane) (PDMS) and poly(ethyl-methyl siloxane) (PEMS). This polymer system has been chosen because of its conveniently located lower miscibility gap with a critical temperature that can easily be adjusted within the experimentally interesting range between room temperature and 100 °C by a suitable choice of the molar masses [81, 82], Furthermore, extensive characterization work has already been done for PDMS/PEMS blends, including the determination of activation energies and Flory-Huggins interaction parameters [7, 8, 83, 84],... 

IGC was used to determine the thermodynamic miscibility behavior of several polymer blends polystyrene-poly(n-butyl methacrylate), poly(vinylidene fluoride)-poly(methyl methacrylate), and polystyrene-poly(2,6-dimethyl-1,4-phenylene oxide) blends. Specific retention volumes were measured for a variety of probes in pure and mixed stationary phases of the molten polymers, and Flory-Huggins interaction parameters were calculated. A generally consistent and realistic measure of the polymer-polymer interaction can be obtained with this technique. 

Predicting blend miscibility correctly is, however, often considerably more challenging than one might guess by looking at the equations given above or even their somewhat more refined versions. Flory-Huggins interaction parameters, their more elaborate versions, and alternative methods such as the equation-of-state theories [9] discussed in Section 3.E, all provide correct predictions in many cases, but unfortunately provide incorrect predictions in many other cases. 

If Rab lies below a certain threshold Ro, the substances are predicted to be miscible, i. e.the polymer is predicted to be soluble in the solvent. On the other hand, the solvent will neither dissolve nor swell the solute in case of Rab Ro- Furthermore, the Hansen solubility parameters can be used for estimating the Flory-Huggins interaction parameter of two polymers... 

For a mixture of low molecular constituents, n-propanol and u-nonane, it was observed not only negative deviation of surface tension from linear variation with composition, but also a minimum in surface tension (Gaman et al., 2005). Figure 6 shows variation of surface tension with composition of the mixture. Similar behaviour was found for the miscible blend of poly(methyl acrylate) (PMA) and poly(ethylene oxide) (PEO) (Pefferkometal., 2010). As far as the author is aware, this is first time that an extreme value for surface tension was found in a miscible polymer blend. The polymers used had number average molecular masses of A/ 5000 g/mol. Blends of PMA and PEO of those low molecular masses are completely miscible (Pedemonte and Buigisi, 1994). The Flory-Huggins interaction parameter was determined from PVT data io x 003 at 120 °C (Pefferkom et al., 2010). 

Figure 4.24. Diffusion coefficients as functions of the composition in the miscible blend polystyrene-poly(xylenyl ether) (PS-PXE) at a temperature 66 °C above the (concentration-dependent) glass transition temperature of the blend, measured by forward recoil spectrometry. Squares represent tracer diffusion coefficients of PXE (VpxE = 292), circles the tracer diffusion coefficients of PS and diamonds the mutual diffusion coefficient. The upper solid line is the prediction of equation (4.4.11) using the smoothed curves through the experimental points for the tracer diffusion coefficients and an experimentally measured value of the Flory-Huggins interaction parameter. The dashed line is the prediction of equation (4.4.11), neglecting the effect of non-ideality of mixing, illustrating the substantial thermodynamic enhancement of the mutual diffusion coefficient in this miscible system. After Composto et al. (1988).

The effect of polymer-polymer interactions on the miscibility and macroscopic properties of PVC/PMMA, PVC/PS, and PMMA/PS blends were studied and the miscibility of the components was characterized by the Flory-Huggins interaction parameter or by quantities related to it by Fekete et al. (Fekete et al. 2005). The comparison of interaction parameters determined by different methods indicates that PVC and PMMA are nearly miscible, while PS is immiscible either with PMMA or with PVC at all compositions. Hory-Huggins interaction parameters calculated from equihbrium methanol uptake (y jj) are plotted as a function of composition in Fig. 10.24. The negative values obtained for the PVC/PMMA blends hint at complete miscibility, although x,2 depends on composition which indicates limited miscibility. The positive interaction parameters determined for the PVC/PS and PMMA/PS blends suggest immiscibility. 

Miscible CTystaUine/amorphous polymer blends such as PLA/PVC blends have been widely investigated, and oriented crystallization has also been applied to some miscible ciystalline/amorphous polymer blends. For miscible blends containing semicrystaUine polymers, analysis of the melting point depression is widely used to estimate the Flory-Huggins interaction parameter (x). 

Blends of AMS-AN copolymers with PVC are used to increase the heat resistance of the product. Blends of PVC and AMS-AN copolymers were formed by precipitation with THF solution into methanol. Miscible blends were found for copolymers of AMS-AN with AN composition containing 11.9-30.0 wt%. Phase separation temperatures were noted by annealing and DSC methods. Phase separation temperatures below 130°C were found. Using the characteristic EOS parameters listed in Table 3.4 and the phase separation temperatures that were measured, the AP values were calculated for the blend system. These values were found to be AP nvc = 4.30 cal/cc APamsvc = 0-26 cal/cc and APan,ams = 8.6 cal/cc. The Flory-Huggins interaction parameters at 130°C were calculated and B Nyc = 4.22 cal/cc B msvc = 0-37 cal/cc Bams,an = 8.04 cal/cc. The binary interaction parameter of the copolymer-homopolymer blend for AMS-AN copolymer and PVC homopolymer for various AN compositions in the copolymer at various volume fractions in the blend is shown in Figure 3.7. 

Miscibility with polymer estimated by Flory Huggins interaction parameter and negative Gibbs free energy. 

Tambasco M, Lipson JEG, Higgins JS (2006) Blend miscibility and the Flory Huggins interaction parameter a critical examination. Macromolecules 39(14) 4860-4868... 

Figure 18 shows the plots of the Flory-Huggins interaction parameters against PEO concentration at fixed temperature (T=400K) under different pressures. It is shown that y reduces with pressure at the fixed PEO concentration in the mixture, which is consistent with the experimental measured result that PEO/P(EO-b-DMS) system shows pressure-induced miscibility behavior. 

From these results calculated, the relations of temperature, pressure, and concentration of PEO/P(EO-b-DMS) mixtures are presented. The influence of pressure on calculated Flory-Huggins interaction parameter of PEO/P(EO-b-DMS) mixtures shows that Flory-Huggins interaction parameter deduces on raising the pressure, i.e., miscibility is enhanced. 

It should be remembered that there are many cases where the measurement of interactions is of importance. SANS has been widely used for the study of polymer blends. A simple extension of the theory gives the following expression for the scattering from a blend of two miscible polymers with a Flory-Huggins interaction parameter... 

PLLA/EVA 85 blends were miscible, determined by Tg, equilibrium T and G. The Flory-Huggins interaction parameter was negative. 

The Cj values of the phase separation with complicated patterns are measured and plotted in Figure 15.48 these data show that the Q value for the system with the block copolymer is 7.69E-01, which is higher than for the system without a block copolymer when the attraction forces are the same. The decrease in the Flory-Huggins interaction parameter increased miscibility of the polymers, which in turn decreased the miscibility gap of the polymers (as shown in Figure 15.4). At... 

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