PVT behavior of polymer melts

Dee and Walstf developed a modified version of Prigogine s cell model that provides an excellent description of the PVT-behavior of polymer melts ... 

Given a reliable PVT description of polymer melts and their mixtures, the equilibrium behavior of a polymer with a gas phase was examined [Xie et al., 1992], During the last 20 years, studies of gas polymer sorption enjoyed great advances on two fronts ... 

In comparison to a conventional polymer and l.c. mentioned above, we will now discuss the PVT behavior of a l.c. side chain polymer, which has linked mesogenic moieties as side chains, and is very similar to the previous monomer. The experimental results are shown in Fig. 5. It is obvious, that the phase behavior of the l.c. polymer differs from that of a 1-l.c. and amorphous polymer. At high temperature we observe a transformation from the isotropic polymer melt into the l.c. phase, indicated by the jump in the V(T) curve. At low temperatures no crystallisation is observed but the bend in the curves signifies a glass transition. Obviously the phase behaviour is determined by the combination of l.c. and polymer properties. 

Equation of State. A number of modeling studies of amorphous polymers have included PVT behavior, either as an end in itself, as a means to validate the potential ftinctions, or to investigate other aspects of polsrmer behavior (411). Polymer melts and glasses that have been studied in some detail include polyethylene (23,370,412), poly(dimethylsiloxane) (413), poly(ethylene oxide) (414), and poly(ethylene terephthalate) (78). Dendrimers having a variety of generations have been compared with linear chains in the respect of their equation of state by means of a tangent hard sphere model by Lue (415). 

Because polymer melt PVT-behavior depends only slightly on polymer molar mass above the oligomeric region, usually no information is given in the original literature for the average molar mass of the polymers. 

The first static property characterizing the system is the pVT behavior, which was already discussed in the last section. Besides this thermodynamic information, an amorphous polymer melt is mainly characterized through two types of structural information the single chain structure factor and the overall structure factor of the melt. 

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