Size-dependent mechanical behavior of free-standing glassy polymer thin films

Xia, Wenjie; Keten, Sinan

doi:10.1557/jmr.2014.289

Cited by 24 publications

(23 citation statements)

References 51 publications

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“…T g depression observed in thin films relative to the bulk is mainly attributed to the free‐surface‐induced enhancement of segmental mobility and shift of chain relaxation . Previous experiments and molecular simulations have consistently demonstrated that the free‐surface effects on thin film T g are influenced by factors relevant to polymer chain relaxation and dynamics, such as film thickness, chain rigidity, cohesive interactions, and others . Among these factors, the role of molecular weight (MW) effects on T g ‐confinement behavior has been studied experimentally, and has also led to theoretical models such as de Gennes' sliding motion mechanism and the delayed glassification model …”

Section: Introductionmentioning

confidence: 99%

“…

relevant to polymer chain relaxation and dynamics, such as fi lm thickness, [ 5,7,8 ] chain rigidity, [ 9,10 ] cohesive interactions, [ 11,12 ] and others. [ 13 ] Among these factors, the role of molecular weight (MW) effects on T g -confi nement behavior has been studied experimentally, [14][15][16][17] and has also led to theoretical models such as de Gennes' sliding motion mechanism [ 18 ] and the delayed glassifi cation model.

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mentioning

confidence: 99%

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Molecular Weight Effects on the Glass Transition and Confinement Behavior of Polymer Thin Films

Xia

Hsu

Keten

2015

Macromol. Rapid Commun.

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Nanoscale polymer thin films exhibit strong confinement effects on Tg arising from free surfaces. However, the coupled influence of molecular weight (MW) and surface effects on Tg is not well understood for low MW film systems below the entanglement length. Utilizing atomistically informed coarse-grained molecular dynamics simulations for poly(methyl methacrylate) (PMMA), it is demonstrated that the decrease in free-standing film Tg with respect to bulk is more significant for low MW compared to high MW systems. Investigation of the local interfacial properties reveals that the increase in the local free volume near the free surface is greater for low MW, explaining the MW dependence of Tg -confinement behaviors. These findings corroborate recent experiments on low MW films, and highlight the relationship between nanoconfinement phenomena and local free volume effects arising from free surfaces.

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Section: Introductionmentioning

confidence: 99%

“…

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mentioning

confidence: 99%

Molecular Weight Effects on the Glass Transition and Confinement Behavior of Polymer Thin Films

Xia

Hsu

Keten

2015

Macromol. Rapid Commun.

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“…The loading rate is around 1 Â 10 7 s À1 , falling into the conventional strain rate regime (10 7 to 10 9 s À1 ) as commonly used in molecular dynamics studies. [71][72][73] To eliminate the effect of thermal uctuations, temperature was controlled at around 1 K. Unless otherwise stated, time integration was performed on Nose-Hoover style non-Hamiltonian equations of motion from the isothermal-isobaric (NPT) ensemble, 74 in which the time step was set to 1 fs for both stability and accuracy. All the simulations were performed by implementing a parallel solver for molecular dynamics LAMMPS, 75 and the results were visualized through the OVITO 76 package.…”

Section: Computational Methods and Modelsmentioning

confidence: 99%

Mechanical anisotropy of two-dimensional metamaterials: a computational study

et al. 2019

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“…The addition of chemical specificity to coarse grain models has enabled simulations to begin to understand the origins of polymer chemistry dependent thermomechanical behavior under confinement . Simulations have also demonstrated that T g and moduli changes on confinement are not fully correlated, in agreement with surface wrinkling experiments . Coarse grain simulations, in general, provide a great opportunity to learn more about the local mechanical properties in confined systems as the particles can be individually tracked in the simulations to readily determine the mean square displacement < u 2 > through the Debye–Waller factor.…”

Section: Elastic Properties Of Polymer Glasses Under Confinementmentioning

confidence: 97%

Mechanical and viscoelastic properties of confined amorphous polymers

Vogt

2017

J Polym Sci B Polym Phys

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Confinement of polymers to nanoscale dimensions can dramatically impact their physical properties. Substantial efforts have focused on the glass transition temperature (T g ) of polymers confined to thin films, but their mechanical properties are less studied despite their technological importance. In this review, challenges with mechanical measurements of polymer thin films are discussed along with novel metrologies that provide insight into their mechanical properties. A comparison of experimental measurements, simulations and theory provide several general conclusions about the mechanical properties under confinement. Confinement impacts the elastic modulus, rubbery compliance and viscosity of polystyrene, the archetypal polymer for confinement, but the confinement effect appears to depend on the measurement technique. This effect may be due to the details of averaging of gradients in properties that are dependent on the measurement details. Routes to minimize confinement effects are addressed. Despite progress in the measurements of mechanical properties of polymer thin films, there remain unresolved questions about the impact of confinement, which we highlight at the end of this review. 1,2 These concerns persist for polymeric nanostructures, where mechanical properties are critical to feature stability. 3 The mechanical properties of many polymers are dependent on their processing history,

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Size-dependent mechanical behavior of free-standing glassy polymer thin films

Abstract: Abstract

Cited by 24 publications

References 51 publications

Molecular Weight Effects on the Glass Transition and Confinement Behavior of Polymer Thin Films

Molecular Weight Effects on the Glass Transition and Confinement Behavior of Polymer Thin Films

Mechanical anisotropy of two-dimensional metamaterials: a computational study

Mechanical and viscoelastic properties of confined amorphous polymers

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