Solid–liquid equilibria of crystalline and semi-crystalline monodisperse polymers, taking into account the molecular architecture by application of the lattice cluster theory

Abstract

In this work, an old theory for the melting of linear, semi-crystalline polymers, developed by Flory in 1949, is rediscovered and extended to branched polymers. The extension is realised by the incorporation of the lattice cluster theory, which is able to model polymers with an arbitrary architecture. The final working equation describing the melting of a branched semi-crystalline polymer can be solved for the melting temperature analytically. This new equation permits the theoretical investigation of different impact factors on the melting temperature in the case of branched semi-crystalline polymer, for instance the influence of molecular weight on the structural variables that describe the crystalline state. It could be shown that the extension leads to a better description of experimental data for the melting of high-density polyethylene taken from the literature than the original equation of linear semi-crystalline polymers. However, the comparison with experimental data makes it clear that the incorporation of polydispersity in the theoretical framework is needed.

Keywords:

• solid–liquid equilibrium
• lattice cluster theory
• melting temperature of semi-crystalline polymers
• impact of branching
• degree of crystallinity