Thermodynamics of melting

In this section, the upper temperature limit of the crystalline state is explored on the basis of experimental data on the thermodynamics of melting, extrapolated to equilibrium. The more common nonequilibrium melting will see its final discussion in Sects. 6.2 and 7.2. The other condensed states of macromolecules, the mesophases, glasses, and melts are treated in Sects. 5.5 and 5.6. Much less is known about them than about the crystals. 

This discussion of the thermodynamics of melting reveals a rather simple theory with good predictive capability for the melting parameters. The heat capacities are also well linked to the underlying molecular motion, and various quantitative baselines can be generated. Only with such quantitative information is it possible to analyse the common deviations from equilibrium. Section 2.2 will expand this discussion to non-equilibrium systems. 

The thermodynamics of melting in polymers was developed by Flory and his co-workers (145-147). To a first approximation, the melting point depression depends on the mole fraction of impurity, Xb, the mole fraction of crys-talUzable polymer being Xa. Substituting Xa for a in equation (6.38),... 

Melt growth is the formation of a crystalline solid from a liquid phase that has essentially the same composition as the solid. If the composition of the liquid shows a larger deviation from that of the solid one deals with solution growth. Fundamentals of thermodynamics of melt growth can be found, e.g. in (15). 

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