Heterotypic Imine Cross-links Reshape Phase Behavior and Relaxations in Polystyrene/Poly(ethylene glycol) Vitrimer Blends
Year: 2026
Type: preprint
Abstract: Converting an immiscible polymer blend into a vitrimer is a powerful strategy for enhancing miscibility while still preserving viscoelasticity. In vitrimer blends, the chains bear dynamic covalent cross-links that undergo associative exchange – new bonds form before old bonds break, permitting the blend to maintain both network connectivity and topological fluidity. Recent studies have demonstrated that vitrimer blend phase behavior results from competition between homotypic cross-links between identical polymers and heterotypic cross-links between dissimilar species. In this work, we investigate binary vitrimer blends in which the two polymer components exclusively form heterotypic linkages. The blends are composed of a polystyrene (PS) copolymer and a telechelic poly(ethylene glycol) (PEG) connected by dynamic imine linkages. We prepare blends with varying PEG weight fractions and chain lengths. In contrast to classical Flory-Huggins theory, which predicts PS and PEG are immiscible at ambient temperature, hybrid molecular dynamics/Monte Carlo simulations, experiments, and theory demonstrate that PS/PEG vitrimer blends assemble into a stoichiometrically balanced network that coexists with a PEG-rich domain – phase behavior analogous to off-eutectic metal alloys. Dynamic cross-linking produces fast and slow relaxation regimes, enhancing the vitrimer blend elasticity relative to linear and graft copolymer blend controls. Yet, the rheological activation energies of the linear, graft copolymer, and vitrimer blends are the same, indicating that the temperature dependence of the slow relaxation regime does not originate from the local energy barrier for imine exchange. By harnessing the combinatorial and conformational entropies of associative exchange, the incorporation of heterotypic cross-links offers a simple and versatile approach to compatibilize immiscible polymers.
Source: ChemRxiv
Language: English
Subfield: Polymers and Plastics
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7222035014