Glass transition and fragility of nanosized polymeric fibers and spheres predicted from a surface-controlled model

Nakane, Tatsuki; Tsuzuki, Yuya; Sasaki, Takashi

doi:10.1038/s41428-020-00431-5

Cited by 3 publications

(2 citation statements)

References 57 publications

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“…Furthermore, some simple phenomenological models were proposed, in which cooperative regions with non-compact shapes were assumed [ 27 , 28 , 29 ]. In addition, such phenomenological approaches were extended to explain the size-dependent dynamics in nanosized polymeric materials [ 30 , 31 , 32 ]. However, the origin of the anomalous dynamics and decoupling between quasi-thermodynamic and dynamic observables in nano-confined systems remains a controversial issue in polymer physics [ 33 , 34 , 35 ].…”

Section: Introductionmentioning

confidence: 99%

A Dynamically Correlated Network Model for the Collective Dynamics in Glass-Forming Molecular Liquids and Polymers

2021

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The non-Arrhenius behavior of segmental dynamics in glass-forming liquids is one of the most profound mysteries in soft matter physics. In this article, we propose a dynamically correlated network (DCN) model to understand the growing behavior of dynamically correlated regions during cooling, which leads to the viscous slowdown of supercooled liquids. The fundamental concept of the model is that the cooperative region of collective motions has a network structure that consists of string-like parts, and networks of various sizes interpenetrate each other. Each segment undergoes dynamical coupling with its neighboring segments via a finite binding energy. Monte Carlo simulations showed that the fractal dimension of the DCNs generated at different temperatures increased and their size distribution became broader with decreasing temperature. The segmental relaxation time was evaluated based on a power law with four different exponents for the activation energy of rearrangement with respect to the DCN size. The results of the present DCN model are consistent with the experimental results for various materials of molecular and polymeric liquids.

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Section: Introductionmentioning

confidence: 99%

A Dynamically Correlated Network Model for the Collective Dynamics in Glass-Forming Molecular Liquids and Polymers

2021

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“…For example, the T g of free-standing polystyrene (PS) films begins to deviate from the bulk value when the film thickness is less than several hundred nanometers. , T g decreased with decreasing thickness, and the value for a film thickness of several tens of nanometers was found to be several tens of kelvin lower than that of the bulk. The decrease in T g may be due to the enhanced mobility of the polymer chains near the free surface compared to the bulk. ,− This effect is expected to increase with decreasing thickness (increasing the volume-to-surface ratio). − The presence of a mobile layer at the surface has been experimentally demonstrated in various polymeric systems. , In general, the relaxation time of the surface layer is shorter than that of the middle bulk-like region by orders of magnitude. ,, …”

Section: Introductionmentioning

confidence: 99%

Thickness Dependence of Segmental Dynamics in Free-Standing Thin Films Predicted by a Dynamically Correlated Network Model

Nakane

Sasaki

2023

J. Phys. Chem. B

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The anomalous dynamics and glass transition behaviors of supercooled liquids under nanoconfinement, such as ultrathin polymer films, have attracted much attention in recent decades. However, a complete elucidation of this mechanism has not yet been achieved. For the dynamics of bulk materials without confinement, we previously proposed a dynamically correlated network (DCN) model, which was found to agree well with the experimental data. The model assumes that segments with thermal fluctuations are dynamically correlated to their neighbors to form string-like clusters, which eventually grow into networks as temperature decreases. In this study, we applied the DCN model to nanoconfined free-standing films by using a simple cubic lattice sandwiched between two free surface layers consisting of virtual "uncorrelated" segments. The average size of DCNs at lower temperatures decreased with decreasing thickness because of confinement. This trend was associated with a decrease in the percolation temperature at which the size of DCN diverges. It was also revealed that the fractal dimension of the generated DCNs exhibits a peak with respect to temperature. The segmental relaxation time for free-standing polystyrene films was evaluated, and the predicted thickness dependence of the glass transition temperature qualitatively agreed with the experimental data. The results suggest that the concept of DCN is compatible with the dynamics of freestanding thin films.

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DSC investigation of chain cooperativity rearrangements and critical length scale of polybutadiene networks in glass transition range

Grigoraş¹

2022

J Therm Anal Calorim

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Glass transition and fragility of nanosized polymeric fibers and spheres predicted from a surface-controlled model

Cited by 3 publications

References 57 publications

A Dynamically Correlated Network Model for the Collective Dynamics in Glass-Forming Molecular Liquids and Polymers

A Dynamically Correlated Network Model for the Collective Dynamics in Glass-Forming Molecular Liquids and Polymers

Thickness Dependence of Segmental Dynamics in Free-Standing Thin Films Predicted by a Dynamically Correlated Network Model

DSC investigation of chain cooperativity rearrangements and critical length scale of polybutadiene networks in glass transition range

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