Physical origin of the second damping peak in ionomers as traced by enthalpy relaxation

Shi, Gaopeng; Geng, Xiaoning; Liu, Yuanbiao; Wu, Guozhang

doi:10.1016/j.polymer.2023.126543

Cited by 3 publications

(2 citation statements)

References 70 publications

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“…Unlike the weakly interacting secondary or slow modes with homogeneous relaxation dynamics, − segmental (or α-) relaxations subjected to strong intermolecular constraints are typically dynamically heterogeneous with nonlinear, nonexponential, and non-Arrhenius features . The enthalpic effects associated with the vitrification process can be probed by most relaxation spectroscopies, such as enthalpy, dielectric, and mechanical relaxations. , Among them, enthalpy relaxation directly traces the free energy of configurational transitions; it not only captures the pure segmental dynamics − but also quantifies all three dynamically heterogeneous features of α-relaxation . To date, few relaxation modes other than enthalpy relaxation provide such rich information about the relaxation dynamics of glass transition.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Bonding-Induced Alleviation of Topological Constraints in Acrylic Polymers Mixed with Small Molecules

Liu,

Guo,

Jiao

et al. 2024

Macromolecules

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Intermolecular hydrogen bonds (inter-HBs) typically act as transient cross-linkers and can enhance the intermolecular interactions. Herein, we report a counterintuitive scenario that interchain constraints of polyacrylates are alleviated by adding hindered phenols capable of forming strong inter-HB interactions with the host polymer, even if a small molecule-bridged inter-HB network apparently increases the glass transition temperature (T g ) of the hybrids. The less-constrained segmental dynamics is confirmed enthalpically by the enhanced dynamic homogeneity (i.e., an increase in nonlinearity parameter x and stretching exponential parameter β) of α-relaxation together with a remarkable increase in the physical aging rate at (T g − 10) K. Further results clarified that x and β values are primarily governed by the strength of inter-HB interactions (Δυ i ), and a stronger Δυ i results in a larger x or β value. The present work provides solid experimental evidence and new molecular-level insights for the lessconstrained segmental dynamics in such HB-driven hybrids in terms of the balanced flexibility between side groups and the backbone, the reduction of energy barriers hindering the cooperative motions, and the alleviation of long-chain connectivity.

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Section: Introductionmentioning

confidence: 99%

Hydrogen Bonding-Induced Alleviation of Topological Constraints in Acrylic Polymers Mixed with Small Molecules

Liu,

Guo,

Jiao

et al. 2024

Macromolecules

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“…Ionomers are another class of materials used extensively in damping applications. 30–35 The microphase separation of ionic clusters from the backbone gives rise to heterogeneity which leads to broader loss tangents and efficient dissipation. Such clusters can also exchange ionic groups, which ultimately leads to flow and a dynamic process that can lead to an increase in tan δ .…”

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confidence: 99%

Multiple energy dissipation modes in dynamic polymer networks with neutral and ionic junctions

Jang,

Schroeder,

Evans

2024

Chem. Commun.

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Ionic Interactions Induced Anomalous Segmental Dynamics in Polymer/Salt Complexes

Shi,

Zhang,

Wang

et al. 2024

Macromolecules

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Dynamic fragility (m) is reported to be inversely proportional to the stretching parameter (β) in many cases. Herein, their relation is further investigated in polyacrylate/salt complexes with ionic interactions. The introduction of metallic ions leads to a decreased enthalpy hysteresis and increased storage modulus at the glassy state, revealing that the ionic interactions act as physical cross-linkers. Further results found a reduced β value and a larger difference in relaxation time between segmental and secondary relaxation. Surprisingly, an anomalous decrease of fragility accompanied by the increase of the glass transition temperature is observed in all complexes. Moreover, the m value further decreases for the α′-relaxation corresponding to the restricted motions in the vicinity of ionic clusters in complex with flexible chains. We suppose that the polarities of metallic ions make extra contributions to the enthalpy change of segmental motions, thereby playing a decisive role in the activation free energy of segmental cooperative rearrangement. Most importantly, the glass transition width can be broadened significantly given that m and β decrease simultaneously, thus providing a new strategy to fabricate high-performance damping materials.

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Physical origin of the second damping peak in ionomers as traced by enthalpy relaxation

Cited by 3 publications

References 70 publications

Hydrogen Bonding-Induced Alleviation of Topological Constraints in Acrylic Polymers Mixed with Small Molecules

Hydrogen Bonding-Induced Alleviation of Topological Constraints in Acrylic Polymers Mixed with Small Molecules

Multiple energy dissipation modes in dynamic polymer networks with neutral and ionic junctions

Ionic Interactions Induced Anomalous Segmental Dynamics in Polymer/Salt Complexes

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