Phase behavior, self-assembly, and interfacial tension of a dynamically linked polymer blend

Area of Science:

• Polymer Science
• Materials Chemistry
• Computational Materials Science

Background:

• Compatibilizing immiscible polymer blends is crucial for enhancing polymer recycling.
• Dynamic cross-links (bonds with finite lifetimes) offer a promising strategy for blend compatibilization.

Purpose of the Study:

• To systematically investigate the impact of dynamic cross-linking on polymer blend phase behavior, self-assembly, and surface tension using molecular dynamics simulations.
• To explore the competing effects of inter-species versus self-cross-links on blend properties.

Main Methods:

• Implementation of a Metropolis-based algorithm for creating reversible dynamic bonds in molecular dynamics (MD) simulations.
• Analysis of phase behavior, self-assembly, and surface tension under varying dynamic cross-linking conditions.
• Mapping cross-linked chain assembly to a coarse-grained model of patchy particle self-assembly.

Main Results:

• Dynamic cross-linkers between different polymer types decrease phase separation critical temperature and surface tension, indicating improved compatibilization.
• The assembly of cross-linked chains can be modeled as patchy particle self-assembly, with effective sticky sites increasing with chain length.
• A balance between inter-species and self-cross-links neutralizes compatibilization effects; higher self-cross-linking reduces miscibility.

Conclusions:

• Dynamic cross-linking is an effective method for compatibilizing immiscible polymer blends, with significant implications for polymer recycling.
• The specificity and propensity of dynamic bonds are critical factors determining blend miscibility and performance.
• Interfacial density of distinct dynamic cross-links dictates a master curve for surface tension in phase-separated systems.