Thermodynamic Modeling of the Solid–Liquid Phase Transition in Polyethylene Copolymer–Solvent Systems Based on Continuous Thermodynamics and Lattice Cluster Theory

Abstract

In this work, a thermodynamic model is developed based on continuous thermodynamics and lattice cluster theory to describe solid−liquid equilibria of polymer−solvent systems, where the polymer shows a certain molecular architecture, semicrystallinity, and a continuous molecular weight distribution. The new thermodynamic model is validated by predicting the solid− liquid phase behavior of ethylene/1-hexene copolymer−1,2,4-trichlorobenzene mixtures for different short-chain branchings, degrees of crystallinities, and molecular weight distributions. It turned out that this thermodynamic model is capable of capturing the solid− liquid transition zone, where a manifold of solid−liquid equilibria exists, due to the continuous character of the molecular weight distribution. For the first time, the coexistence region of the solid−liquid transition of a polyethylene−solvent system is predicted based on a thermodynamic consistent model. Further model calculations show how the polydisperse nature of the polymer influences the coexistence region in a complex and nonlinear manner, especially in the low-molecular-weight regime. This gives new insights into the solid−liquid phase behavior of polydisperse polymer−solvent mixtures and provides valuable information on the field of polymer crystallization.

Thermomechanical Degradation of Polypropylene – Polystyrene Blends During Extrusion‐Based Melt Blending – A First Survey of Shear‐Induced Molecular Architecture Changes

“…[40] It is concluded by former research works focusing on onedimensional TREF distributions that a shifting of regular- ity distribution to lower temperatures is induced by chain irregularities. [24,26] The more pronounced the chain irregularity is, the more the TREF distribution is shifted to lower temperatures. As a consequence, it can be directly deduced, that the chain irregularity of the PP is increasing with an increasing amount of PS fraction within the blended sample during the extrusion-based blending process.…”

“…In the past, the relationship between crystallization temperature and chain regularity is studied, and models explaining the correlation between crystallization temperature and chain regularity were successfully developed. [24] For more detailed information about correlations of chain regularities and crystallization temperatures in TREF measurements the reader is referred to. [24][25][26] Additionally, the regularity changes of PP can be evaluated precisely and linked directly to fraction-specific molecular weight distribution changes.…”

“…[24] For more detailed information about correlations of chain regularities and crystallization temperatures in TREF measurements the reader is referred to. [24][25][26] Additionally, the regularity changes of PP can be evaluated precisely and linked directly to fraction-specific molecular weight distribution changes. Hence, the bivariate distribution information is gained.…”

Macromolecular Architecture‐Dependent Polymorphous Crystallization Behavior of PVDF in the PVDF/γ‐BL System via Thermally Induced Phase Separation

“…It is known from other polymer solvent systems, e.g., polyethylene-solvent systems, that there is a strong correlation between macromolecular architecture, in terms of molecular weight and branching, and the S-L phase behavior. [32][33][34][35][36] Therefore, the objective of this research is to investigate the impact of the macromolecular architecture of PVDFspecifically, its molecular weight, branching, and regio-defectson its polymorphic crystallization behavior in a low molecular weight PVDF/𝛾-BL system. Due to the high polarity of 𝛾-BL and the comparably low molecular weight of the PVDF, it seems to be an attractive system to be studied in terms of understanding the promotion of the electroactive 𝛾-phase.…”

Lattice-Cluster-Theory-Informed Cross-Fractionation Chromatography Revealing Degree of Crystallinity of Single Macromolecular Species

“…However, gaining access to this relationship could be a key factor in enhancing molecular design capabilities within the context of engineering semicrystalline morphologies. If this relation can be established, a property-originated design can be carried out by controlling architecture with sophisticated fractionation or synthesis methods. − A complex distribution of molecular architectural features (molecular weight and branching) occurs, for instance, in polyethylene. Understanding this complexity is key in terms of establishing tailor-made properties.…”