Continuous thermodynamics of polymer systems

Continuous thermodynamics permits the thermodynamic treatment of systems containing polydisperse polymers by direct use of the continuous distribution function such as is obtained experimentally. To this end, the total structure of chemical thermodynamics is converted to a continuous basis. The most important advantages of continuous thermodynamics when compared with the traditional pseudo-component method are as follows: (1) The arbitrary splitting of the continuous distribution into a number of pseudo-components proves to be an unnecessary introduction of additional errors: (2) In continuous thermodynamics the polymer species are identified by a continuous variable resulting in the possibility to differentiate, to integrate, etc. with respect to this variable; (3) considering the liquid--liquid equilibrium or the polymer fractionation, exact and explicit equations are provided interrelating the distribution functions in the different phases. Only a very small number of equations then need be solved numerically, corresponding to a large reduction of required computer time. These equations contain integrals which for the cloud-point curve/shadow curve problem in many cases may be calculated analytically as a further important simplification. In addition to the liquid--liquid equilibrium, continuous thermodynamics may also be applied to stability considerations enabling the calculation of the spinodal and of the critical point. 48 ref.--AA