Equilibrium melting point molecular weights

S is the thickness of the deposited layer, and CaOe the surface free energy of the lateral and edge faces. Tm is the equilibrium melting point of the polymer and Tc the crystallization temperature. Since chain ends depress the melting point, this, with variations in molecular weight dependence of the growth rates. 

Polymerization in the liquid crystal state involves a major increase in the molecular weight of the polymer, reaching the hundreds of thousands. The thermodynamic equilibrium between the monomer in smectic liquid crystals and the polymer is shifted completely toward formation of the polymer up to the melting point of the crystal (138°C.). The polymerization rate does not change with the degree of conversion... 

The GC route is particularly attractive for it requires no a priori information on the polymer. With the exception of X-ray measurements, most methods of measurement involve a comparison of some property of the polymer, such as density, with that of the totally amorphous or crystalline material. Furthermore neither the mass of polymer in the column nor the flow rate of carrier gas need to be measured since a ratio of retention volumes is computed in Eq. (21). It should be added, however, ttiat for the successful application of the method it is essential that the measured retention volumes correspond effectively to equilibrium bulk sorption, both above and below. Low molecular weight compounds are known to exhibit apparently similar discontinuities in retention diagrams at their melting points but this is to be ascribed to a change in retention mechanism, from surface adsorption for the solid to bulk sorption for the liquid stationary phase. For a detailed discussion of retention characteristics of low molecular weight substances near their transition temperatures the reader is referred to a recent review by McCrea (8J). 

At the melting point of the trimetaphosphate (625° C) ring opening occurs and a polymerization equilibrium is set up in the amorphous phase. The molecular weight distribution which is now random increases... 

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