Non-equilibrium Thermodynamics of Polymer Crystallization

Nucleation and growth are the most important processes in determining the final morphology of the crystallized polymer and consequently the properties of the material. Both processes can be quite conveniently described within the framework of mesoscopic non-equilibrium thermodynamics. 

Mesoscopic non-equilibrium thermodynamics provides a description of activated processes. In the case considered here, when crystallization proceeds by the formation of spherical clusters, the process can be characterized by a coordinate y, which may represent for instance the number of monomers in a cluster, its radius or even a global-order parameter indicating the degree of crystallinity. Polymer crystallization can be viewed as a diffusion process through the free energy barrier that separates the melted phase from the crystalline phase. From mesoscopic non-equilibrium thermodynamics we can analyze the kinetic of the process. Before proceeding to discuss this point, we will illustrate how the theory applies to the study of general activated processes. 

We have shown that mesoscopic non-equilibrium thermodynamics satisfactorily describes the dynamics of activated processes in general and that of polymer crystallization in particular. Identification of the different mesoscopic configurations of the system, when it irreversibly proceeds from the initial to the final phases, through a set of internal coordinates, and application of the scheme of non-equilibrium thermodynamics enable us to derive the non-linear kinetic laws governing the behavior of the system. 

The basic thermodynamic, kinetic, and structural principles which govern the crystallization behavior of polymers have been developed so far. These principles can now be applied to give an understanding of the properties of semicrystalline polymers. There is a continuing interest in understanding the properties of crystalline polymers in terms of structure. Because of the non-equilibrium character of the... 

In the first chapter, an overview of thermodynamic behaviors of non-equilibrium polymers is discussed. In the consecutive chapters, different properties of polymer blends are discussed, including surface tension, transition, crystallization, morphology, and flow behaviors. Miscibility and molecular characterizations of polymer blends are also covered in this book. Applications to various systems are reviewed, and both experimental concerns and references are supplied. 

In contrast to uncharged macromolecules, polyelectrolyte adsorbed on crystals does not exchange freely with non-adsorbed polyelectrolyte in the absence of added electrolyte. This is a result of the electrical repulsion from the adsorbed polymer preventing the close approach of unadsorbed polymers, thus giving a form of kinetic equilibrium rather than thermodynamic equilibrium. 

---