Entanglement Reduction Induced by Geometrical Confinement in Polymer Thin Films

García, Nicolás; Barrat, Jean‐Louis

doi:10.1021/acs.macromol.8b01884

Cited by 31 publications

(37 citation statements)

References 46 publications

(102 reference statements)

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“…In general, there are two main factors that contribute to the nanoconfinement of free‐standing films, the finite‐size effect of a polymer chain and the interface or free surface effect. The finite size effect is related to the diminishing degree of entanglements as a polymer film approaches a thickness of similar size scale to the polymer chain end‐to‐end distance . The free surface effect is vital for thin films as the volume to surface area ratio diminishes until the film becomes dominated by the air–polymer interface (a highly mobile layer) rather than the bulk.…”

Section: Glass Transition For Polymersmentioning

confidence: 99%

“…The finite size effect is related to the diminishing degree of entanglements as a polymer film approaches a thickness of similar size scale to the polymer chain end-to-end distance. [112] The free surface effect is vital for thin films as the volume to surface area ratio diminishes until the film becomes dominated by the air-polymer interface (a highly mobile layer) rather than the bulk. For the free-standing films, because of the finite-size and free surface effect, the T g decreases with film thickness.…”

Section: Nanoconfinement Effectmentioning

confidence: 99%

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Glass Transition Phenomenon for Conjugated Polymers

Qian

Cao

Galuska

et al. 2019

Macro Chemistry & Physics

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Conjugated polymers are emerging as promising building blocks for a broad range of modern applications including skin‐like electronics, wearable optoelectronics, and sensory technologies. In the past three decades, the optical and electronic properties of conjugated polymers have been extensively studied, while their thermomechanical properties, especially the glass transition phenomenon which fundamentally represents the polymer chain dynamics, have received much less attention. Currently, there is a lack of design rules that underpin the glass transition temperature of these semirigid conjugated polymers, putting a constraint on the rational polymer design for flexible stretchable devices and stable polymer glass that is needed for the devices’ long‐term morphology stability. In this review article, the glass transition phenomenon for polymers, glass transition theories, and characterization techniques are first discussed. Then previous studies on the glass transition phenomenon of conjugated polymers are reviewed and a few empirical design rules are proposed to fine‐tune the glass transition temperature for conjugated polymers. The review paper is finished with perspectives on future directions on studying the glass transition phenomena of conjugated polymers. The goal of this perspective is to draw attention to challenges and opportunities of controlling, predicting, and designing polymeric semiconductors, specifically to accommodate their end use.

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Section: Glass Transition For Polymersmentioning

confidence: 99%

Section: Nanoconfinement Effectmentioning

confidence: 99%

Glass Transition Phenomenon for Conjugated Polymers

Qian

Cao

Galuska

et al. 2019

Macro Chemistry & Physics

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“…this behavior is expected to become considerably less realistic since disentanglement and a greater degree of chain swelling are eventually expected 9,66 . Generally if the parameters of a coarse-grained model are changed (e.g.…”

Section: Chain Bond Orientation Correlation Functionmentioning

confidence: 99%

Entanglement dynamics at flat surfaces: Investigations using multi-chain molecular dynamics and a single-chain slip-spring model

Kirk

Wang

Ilg

2019

The Journal of Chemical Physics

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The dynamics of an entangled polymer melt confined in a channel by parallel plates is investigated by Molecular Dynamics (MD) simulations of a detailed, multi-chain model. A primitive path analysis predicts that the density of entanglements remains approximately constant throughout the gap and drops to lower values only in the immediate vicinity of the surface. Based on these observations, we propose a coarse-grained, single-chain slip-spring model with a uniform density of slip-spring anchors and slip-links. The slip-spring model is compared to the Kremer-Grest MD bead-spring model via equilibrium correlation functions of chain orientations. Reasonably good agreement between the single-chain model and the detailed multi-chain model is obtained for chain relaxation dynamics, both away from the surface and for chains whose center of mass positions are at a distance from the surface that is less than the bulk chain radius of gyration, without introducing any additional model parameters. Our results suggest that there is no considerable drop in topological interactions for chains in the vicinity of a single flat surface. We infer from the slip-spring model that the experimental plateau modulus of a confined polymer melt may be different to a corresponding unconfined system even if there is no drop in topological interactions for the confined case.

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“…To complicate matters, the properties of such nanometer-thin polymer films tend to deviate from their bulk properties due to an increasing contribution of the polymer interface 6 , 7 . This accompanies a phenomena known as the finite size effect, which describes the geometrical constraints that occur when the thickness of a polymer film is of the same length scale as the dimensions of an individual polymer coil, characterized by its polymer chain end-to-end distance ( R ee ) 8 , 9 . A prime example of such a thickness-dependent property is the glass transition phenomena in polystyrene (PS) 10 – 13 .…”

Section: Introductionmentioning

confidence: 99%

SMART transfer method to directly compare the mechanical response of water-supported and free-standing ultrathin polymeric films

et al. 2021

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Intrinsic mechanical properties of sub-100 nm thin films are markedly difficult to obtain, yet an ever-growing necessity for emerging fields such as soft organic electronics. To complicate matters, the interfacial contribution plays a major role in such thin films and is often unexplored despite supporting substrates being a main component in current metrologies. Here we present the shear motion assisted robust transfer technique for fabricating free-standing sub-100 nm films and measuring their inherent structural–mechanical properties. We compare these results to water-supported measurements, exploring two phenomena: 1) The influence of confinement on mechanics and 2) the role of water on the mechanical properties of hydrophobic films. Upon confinement, polystyrene films exhibit increased strain at failure, and reduced yield stress, while modulus is reduced only for the thinnest 19 nm film. Water measurements demonstrate subtle differences in mechanics which we elucidate using quartz crystal microbalance and neutron reflectometry.

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Entanglement Reduction Induced by Geometrical Confinement in Polymer Thin Films

Cited by 31 publications

References 46 publications

Glass Transition Phenomenon for Conjugated Polymers

Glass Transition Phenomenon for Conjugated Polymers

Entanglement dynamics at flat surfaces: Investigations using multi-chain molecular dynamics and a single-chain slip-spring model

SMART transfer method to directly compare the mechanical response of water-supported and free-standing ultrathin polymeric films

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