Thermodynamic analysis of spherulitic growth in semi-crystalline poly(ethylene oxide)

A thermodynamic model for the description of spherulitic growth in (semi-) crystalline polymers is
presented. Its validity is restricted to the free growth stage of crystallization. The relevance of the
role played by surface tension in the early stage of the process is pointed out. With the due
approximations the predicted growth rate is found to be consistent with the well-known Avrami
model. As an application, the melting temperatures T, of poly(ethylene oxide) samples of different
molecular weights are derived by fitting the appropriate crystallization thermograms carried out in
isothermal conditions. A linear dependence of T; ' as a function of the inverse polimerization degree
is found, which is consistent with a well-known result of the lattice theory.