Understanding, predicting, and tuning the fragility of vitrimeric polymers

Abstract

Fragility is an empirical property that describes how abruptly a glass-forming material solidifies upon supercooling. The degree of fragility carries important implications for the functionality and processability of a material, as well as for our fundamental understanding of the glass transition. However, the microstructural properties underlying fragility still remain poorly understood. Here, we explain the microstructure-fragility link in vitrimeric networks, a novel type of high-performance polymers with unique bond-swapping functionality and unusual glass-forming behavior. Our results are gained from coarse-grained computer simulations and first-principles Mode-Coupling Theory (MCT) of star-polymer vitrimers. We first demonstrate that the vitrimer fragility can be tuned over an unprecedentedly broad range, from fragile to strong and even superstrong behavior, by decreasing the bulk density. Remarkably, this entire phenomenology can be reproduced by microscopic MCT, thus challenging the conventional belief that existing first-principles theories cannot account for non-fragile behaviors. Our MCT analysis allows us to rationally identify the microstructural origin of the fragile-to-superstrong crossover, which is rooted in the sensitivity of the static structure factor to temperature variations. On the molecular scale, this behavior stems from a change in dominant length scales, switching from repulsive excluded-volume interactions to intrachain attractions as the vitrimer density decreases. Finally, we develop a simplified schematic MCT model which corroborates our microscopically-founded conclusions and which unites our findings with earlier MCT studies. Our work sheds new light on the elusive structure-fragility link in glass-forming matter, and provides a first-principles-based platform for designing novel amorphous materials with an on-demand dynamic response.

References in corpus (47)

• Theoretical perspective on the glass transition and amorphous materials
• Supercooled Liquids for Pedestrians
• Mean field theory of hard sphere glasses and jamming
• Strong scaling of general-purpose molecular dynamics simulations on GPUs
• The role of local structure in dynamical arrest
• Fragilities of Liquids Predicted from the Random First Order Transition Theory of Glasses
• Static and Dynamic Properties of a Viscous Silica Melt Molecular Dynamics Computer Simulations
• Fragile-to-strong transition and polyamorphism in the energy landscape of liquid silica
• The frustration-based approach of supercooled liquids and the glass transition: a review and critical assessment
• Probing the equilibrium dynamics of colloidal hard spheres above the mode-coupling glass transition
• Mode-Coupling Theory (MCT) Lecture Notes
• Is the Fragility of a Liquid Embedded in the Properties of its Glass?
• Glass and Jamming Transitions: From Exact Results to Finite-Dimensional Descriptions
• The Phase Diagram of Star Polymer Solutions
• Mode-Coupling Theory of the Glass Transition: A Primer
• "In silico" synthesis of microgel particles
• Relaxation in a glassy binary mixture: Comparison of the mode-coupling theory to a Brownian dynamics simulation
• Interatomic repulsion softness directly controls the fragility of supercooled metallic melts
• Hopping and the Stokes-Einstein relation breakdown in simple glass formers
• The Debye-Waller factor of liquid silica: Theory and simulation
• Dynamics of vitrimers: defects as a highway to stress relaxation
• Glass transition and random close packing above three dimensions
• The relaxation dynamics of a viscous silica melt: II The intermediate scattering functions
• The microscopic role of deformation in the dynamics of soft colloids
• The glass transition of soft colloids
• Colloidal glass transition: Beyond mode-coupling theory
• Dimensional Study of the Caging Order Parameter at the Glass Transition
• Mode-coupling theory for structural and conformational dynamics of polymer melts
• Anomalous glassy dynamics in simple models of dense biological tissue
• Gel-forming patchy colloids and network glass formers: Thermodynamic and Dynamic analogies
• Why polymer chains in a melt are not random walks
• Microscopic dynamics of supercooled liquids from first principles
• Tuning the fragility of a glassforming liquid by curving space
• Revisiting the slow dynamics of a silica melt using Monte Carlo simulations
• Attractive versus truncated repulsive supercooled liquids: The dynamics is encoded in the pair correlation function
• Why glass elasticity affects the thermodynamics and fragility of super-cooled liquids
• Structural and conformational dynamics of supercooled polymer melts: Insights from first-principles theory and simulations
• Static triplet correlations in glass-forming liquids: A molecular dynamics study
• Supercooled liquids, the glass transition, and computer simulations
• Relaxation Patterns in Supercooled Liquids from Generalized Mode-Coupling Theory
• Efficient sampling of reversible cross-linking polymers: Self-assembly of single-chain polymeric nanoparticles
• Static Properties of a Simulated Supercooled Polymer Melt: Structure Factors, Monomer Distributions Relative to the Center of Mass, and Triple Correlation Functions
• Generalized mode-coupling theory of the glass transition. I. Numerical results for Percus-Yevick hard spheres
• Particle Content of the Nonlinear Sigma Model with Theta-Term: a Lattice Model Investigation
• Flexible confinement leads to multiple relaxation regimes in glassy colloidal liquids
• The Dynamics of Silica Melts under High Pressure: Mode-Coupling Theory Results
• Tuning Pairwise Potential Can Control the Fragility of Glass-Forming Liquids: From Tetrahedral Network to Isotropic Soft Sphere Models

Cited by in corpus (10)

• Entropy-Controlled Cross-Linking in Linker-Mediated Vitrimers
• Fragile Glasses Associated with a Dramatic Drop of Entropy under Supercooling
• Multi-component generalized mode-coupling theory: Predicting dynamics from structure in glassy mixtures
• Generalized Mode-Coupling Theory for Mixtures of Brownian Particles
• Dynamical Susceptibilities Near Ideal Glass Transitions
• Glassy dynamics of a binary Voronoi fluid: A mode-coupling analysis
• Glassy dynamics from generalized mode-coupling theory: existence and uniqueness of solutions for hierarchically coupled integro-differential equations
• Glassy dynamics of sticky hard spheres beyond the mode-coupling regime
• The distinguishable-particle lattice model of glasses in three dimensions
• Associative bond swaps in molecular dynamics