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A new group contribution lattice-fluid equation of state (GCLF-EOS) is described that can accurately predict the activities of solvents in polymer solutions. This equation of state is a modification of the equation of state derived by Panayioutou and Vera (1982), which is based on the lattice statistics developments of Guggenheim (1952). The group contribution modification permits the prediction of solvent activity, given only the structure of the polymer and solvent involved. The GCLF-EOS can accurately predict solvent activities in polystyrene, polyethylene, poly(ethy1ene oxide), poly(ethy1ene glycol), poly(propylene oxide), and poly(viny1 chloride). The model does not perform as well for solvent activities in polyisobutylene due to the inaccurate group contribution values for the quaternary carbon group. IntroductionPolymer processing involves many separation operations that are designed to remove impurities, solvents, and monomers. Phase equilibrium properties of polymer solutions affect how these processing steps can be carried out. If possible, equations of state are preferred over activity coefficient models for calculation of phase equilibria. Equations of state can provide an accurate, consistent model for all phases and conditions. The equation of state, however, must be able to describe all phases involved. It is a difficult task to derive a general equation of state that is applicable to a wide variety of molecules for both vapor and liquid phases.Many The group contribution method developed in this research can be applied in principle to any homopolymer, random copolymer, or alternating copolymer that can be constructed from the available group contributions, although only systems involving homopolymers are presented in this paper. Block copolymers and cross-linked polymers cannot be treated with this method. Branching in a molecule such as polyethylene must be specified in terms of number of branches per 1,000 carbon atoms in the main chain to correctly assign the groups in the molecule. Pure-Component Group Contribution Equation of StateThe basis of the random hole group contribution lattice-fluid equation of state (GTCLF-EOS) is a lattice-fluid model previously developed by Panayiotou and Vera (1982). Several workers have developed an equation of state based on the lattice fluid,

A unique method has been developed to experimentally observe mutual diffusion of poly-(ethyleneco-methacrylic acid) (EMAA) and poly(viny1 methyl ether) (PVME) using conventional transmission FTIR spectroscopy. Using closed boundary conditions and assuming a composition-independent diffusion coefficient, a value of D = 6.5 X 1W6 cm2/s was determined at 110 "C.

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