Onset of Plasticity in Thin Polystyrene Films

Gurmessa, Bekele; Croll, Andrew B.

doi:10.1103/physrevlett.110.074301

Cited by 30 publications

(36 citation statements)

References 33 publications

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“…Fig. 4 shows the critical strain for plasticity as a function of film thickness for both PS (the same data as in reference 20 adjusted with the scaling prefactor discussed above) and homopolymer P2VP. The behavior of P2VP largely mirrors that of PS films.…”

Section: Resultsmentioning

confidence: 99%

“…In an attempt to fill this gap, we have used a recently-developed localized-bending methodology to examine the early stages of plastic failure in a model block copolymer, polystyrene-b-poly(2-vinylpyridine) or PS-P2VP, and the two homopolymers used to make it up (polystyrene, PS, and poly(2-vinylpyridine), P2VP). 20 An increase in the critical strain for plastic deformation was observed in all samples as film thickness is reduced. The critical strain recorded for the symmetric block copolymer fell halfway between the values recorded for the two homopolymers, but only after sufficient annealing for significant microphase separation to take place.…”

Section: Introductionmentioning

confidence: 85%

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Influence of Thin Film Confinement on Surface Plasticity in Polystyrene and Poly(2-vinylpyridine) Homopolymer and Block Copolymer Films

Gurmessa

Croll

2015

Macromolecules

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Thin block copolymer films have attracted considerable academic attention because of their ability to self-assemble into various microstructures, many of which have potential technological applications. Despite the ongoing interest, little effort has focused on the onset of plasticity and failure which are important factors for the eventual adoption of these materials. Here we use delamination to impart a quantifiable local stain on thin films of homopolymer polystyrene and poly(2-vinylpyridine), as well as block copolymers made of styrene and 2-vinylpyridine.Direct observation of the damage caused by bending with atomic force microscopy and laser scanning confocal microscopy, leads to the identification of a critical strain for the onset of plasticity. Moving beyond our initial scaling analysis, the more quantitative analysis presented here shows strain levels for thick films to be comparable to bulk measurements. Monitoring the critical strain leads to several observations: 1.) as-cast PS-P2VP has low critical strain, 2.) annealing slowly increases critical strain as microstructural ordering takes place, and 3.) similar to the homopolymer, both as cast and ordered films both show increasing critical strain under confinement.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 85%

Influence of Thin Film Confinement on Surface Plasticity in Polystyrene and Poly(2-vinylpyridine) Homopolymer and Block Copolymer Films

Gurmessa

Croll

2015

Macromolecules

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“…It has been known that nanoconfinement can alter many physical properties of polymers, including decrease in mechanical modulus (16,17), glass transition temperature (18,19), and increase in mechanical ductility (20)(21)(22). These changes are primarily due to the enhanced polymer chain dynamics in the amorphous regions (23)(24)(25) and the restricted growth of large crystallites (26).…”

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confidence: 99%

Highly stretchable polymer semiconductor films through the nanoconfinement effect

Wang

et al. 2017

Science

967

901

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Soft and conformable wearable electronics require stretchable semiconductors, but existing ones typically sacrifice charge transport mobility to achieve stretchability. We explore a concept based on the nanoconfinement of polymers to substantially improve the stretchability of polymer semiconductors, without affecting charge transport mobility. The increased polymer chain dynamics under nanoconfinement significantly reduces the modulus of the conjugated polymer and largely delays the onset of crack formation under strain. As a result, our fabricated semiconducting film can be stretched up to 100% strain without affecting mobility, retaining values comparable to that of amorphous silicon. The fully stretchable transistors exhibit high biaxial stretchability with minimal change in on current even when poked with a sharp object. We demonstrate a skinlike finger-wearable driver for a light-emitting diode.

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“…Actually, it has been known for some time instabilities can lead to a variety of patterns in a mechanical system. For example, for a thin layer coated to a compliant substrate and a core/shell system, various highly ordered patterns can occur due to the mismatched deformation( [8], [9], [10], [11], [12]). Also for a thin shell or plate, wrinkling will occur when the structure is under indentation( [13], [14]).…”

Section: Background and Modelmentioning

confidence: 99%

Critical thickness ratio for buckled and wrinkled fruits and vegetables

Dai¹,

Liu²

2014

EPL

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Fruits and vegetables are usually composed of exocarp and sarcocarp and they take a variety of shapes when they are ripe. Buckled and wrinkled fruits and vegetables are often observed. This work aims at establishing the geometrical constraint for buckled and wrinkled shapes based on a mechanical model. The mismatch of expansion rate between the exocarp and sarcocarp can produce a compressive stress on the exocarp. We model a fruit/vegetable with exocarp and sarcocarp as a hyperelastic layer-substrate structure subjected to uniaxial compression. The derived bifurcation condition contains both geometrical and material constants. However, a careful analysis on this condition leads to the finding of a critical thickness ratio which separates the buckling and wrinkling modes, and remarkably, which is independent of the material stiffnesses. More specifically, it is found that if the thickness ratio is smaller than this critical value a fruit/vegetable should be in a buckling mode (under a sufficient stress); if a fruit/vegetable in a wrinkled shape the thickness ratio is always larger than this critical value. To verify the theoretical prediction, we consider four types of buckled fruits/vegetables and four types of wrinkled fruits/vegetables with three samples in each type. The geometrical parameters for the 24 samples are measured and it is found that indeed all the data fall into the theoretically predicted buckling or wrinkling domains. Some practical applications based on this critical thickness ratio are briefly discussed. BACKGROUND AND MODELMany vegetables and fruits contain exocarp and sarcocarp and usually exocarp is stiffer than sarcocarp in order to protect it. There are many different morphologies for fruits and vegetables, and in particular wrinkled and globally buckled shapes are often observed, e.g. wrinkled pumpkins and buckled cucumbers (see Figs. 6 and 7). Why a fruit/vegetable takes the final shape when they ripe may be due to many different factors during the growth process. But, mechanical forces alone can play a very important role for determining the geometry of vegetables and fruits (cf. [1]). Now, it has been understood that the out layer of plant meristems often expands faster than the inner one, leading to to the whole structure under compression on the interface (see [1] and [2]). In fact, a newborn fruit or vegetable has a smooth surface, and only after the certain period of growth, the morphology features occur and remain since (cf.[3] to see details). Over the past decades or so, many authors have used purely mechanical models to study patterns in biological objects, e.g., fingerprint formation by using the Von Karman's equations ([4], [5]) and pattern formation in plants through shell instability ([6]) and shapes of sympetalous flowers through growth of a thin elastic sheet ([7]).Actually, it has been known for some time instabilities can lead to a variety of patterns in a mechanical system. For example, for a thin layer coated to a compliant substrate and a core/shell system, various...

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Onset of Plasticity in Thin Polystyrene Films

Cited by 30 publications

References 33 publications

Influence of Thin Film Confinement on Surface Plasticity in Polystyrene and Poly(2-vinylpyridine) Homopolymer and Block Copolymer Films

Influence of Thin Film Confinement on Surface Plasticity in Polystyrene and Poly(2-vinylpyridine) Homopolymer and Block Copolymer Films

Highly stretchable polymer semiconductor films through the nanoconfinement effect

Critical thickness ratio for buckled and wrinkled fruits and vegetables

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