Miscibility of polymer blends

The lattice fluid equation-of-state theory for polymers, polymer solutions, and polymer mixtures is a useful tool which can provide information on equa-tion-of-state properties, and also allows prediction of surface tension of polymers, phase stability of polymer blends, etc. [17-20]. The theory uses empty lattice sites to account for free volume, and therefore one may treat volume changes upon mixing, which are not possible in the Flory-Huggins theory. As a result, lower critical solution temperature (LCST) behaviors can, in principle, be described in polymer systems which interact chiefly through dispersion forces [17]. The equation-of-state theory involves characteristic parameters, p, v, and T, which have to be determined from experimental data. The least-squares fitting of density data as a function of temperature and pressure yields a set of parameters which best represent the data over the temperature and pressure ranges considered [21]. The method,however,requires tedious experiments to deter- 

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Coleman, M.M., Graf, J.F., and Painter, P.C., Specific Interactions and the Miscibility of Polymer Blends, Technomic Publishing, Lancaster, 1991. 

Freed, K. F. and Dudowicz, J. Influence of Monomer Molecular Structure on the Miscibility of Polymer Blends. Vol. 183, pp. 63-126. 

Coleman MM, Graf JF, Painter PC. Specific interactions and the miscibility of polymer blends. Lancaster (PA) Technomic 1991. 

Coleman, M. M., J. F. Graf, and P. C. Painter. ISKplecific Interactions and the Miscibility of Polymer Blends. Lancaster Technomic Publishing Company. 

M.M. Coleman, J.F. Graf and P.C. Painter, Specific Interactions and Miscibility of Polymer Blends, Technomic Publishing Company, Lancaster, PA, 1991. 

As reviewed in the previous section, measurements of Ti and Tip can provide an estimation of the length scale of miscibility of polymer blends. Compared with such kinds of experiments, the results of the spin-diffusion experiments are more quantitative and straightforward. The accuracy of the results of spin-diffusion experiments relies, to a large extent, on the values of spin-diffusion coefficients (7)) employed in calculation of the constituent phase components. Despite efforts that have been made, there still lacks a suitably applicable method of directly measuring the spin-diffusion coefficients, at least for polymers. For rigid polymer below Tg, 0.8 nm /ms has been turned out to be a reliable value of spin-diffusion coefficient. The difficulty left then concerns how to determine the coefficient of the mobile phase, which is very sample dependent. Recently, through studies on diblock copolymers and blend samples with known domain sizes, Mellinger et al established empirical relations between the T2 and D as follows ... 

The effect of dissolved CO2 on the miscibility of polymer blends and on phase transitions of block copolymers has been measured with spectroscopy and scattering (40). The shifts in phase diagrams with CO2 pressure can be pronounced. Polymer blends may be trapped kinetically in metastable states before they have time to phase separate. Metastable polymer blends of polycarbonate (PC) and poly(styrene-cn-acrylonitiile) were formed with liquid and supercritical fluid CO2 in the PCA process, without the need for a surfactant. Because of the rapid mass transfer between the CO2 phase and the solution phase, the blends were trapped in a metastable state before they... 

Harismiadis, V.I. et al.. Miscibility of polymer blends with engineering models, AIChE J., 42,3170,1996. Pappa, G.D., Voutsas, E.C., and Tassios, D.P., Prediction of solvent activities in polymer solutions with simple group-contribution models, Ind. Eng. Chem. Res., 38, 4975, 1999. 

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