A Theory for Solubility of Semicrystalline and Branched Polymers in One Solvent

• Published in: Macromolecules Vol. 47; no. 21; pp. 7625 - 7636
• Main Authors: Fischlschweiger, Michael, Enders, Sabine
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 11.11.2014
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Solution and gel properties; Solvent effect; Structure effect; Thermodynamic model; Branched polymer; Binary system; Solubility; Theoretical study; Liquid solid equilibrium; Semicrystalline polymer; Modeling; Solvent
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma501440x

Chain architecture and degree of crystallinity of polymers strongly influence the solid–liquid equilibrium of binary polymer solvent systems. Especially, for explaining the principle of common polymer separation techniques a fair prediction of solid–liquid equilibria of polymer solvent systems is of crucial importance. Herein, based on the framework of lattice cluster theory, a theory is developed considering additional configurational entropy contributions due to the semicrystalline nature and molecular architecture of polymers. For calculating solid–liquid equilibria of semicrystalline polymer solvent systems an analytical equation is derived. Model calculations are performed to study the impact of molecular mass, molecular architecture, degree of crystallinity, and solvent size and structure on solid–liquid equilibria of polymer solvent systems. The model calculation results are discussed qualitatively in terms of experimental observations in thermal fractionation techniques. The theory is further applied to calculate solid–liquid equilibria of fractions of ethylene/α-olefins with different amounts of comonomers dissolved in 1,2,4-trichlorobenzene and compared with experimental CRYSTAF data. We could show that the theory enables the calculation of solid–liquid equilibria of polymer solvent systems, where chain architecture of both polymer and solvent and the semicrystallinity are incorporated. The work contributes to the understanding of polymer solubility. Hence, valuable clues are offered about the principal mechanism of thermal polymer separation techniques, and further a solid base to suggest improvements for experimental separation methods is provided.