Directly Measuring the Complete Stress–Strain Response of Ultrathin Polymer Films

Liu, Yujie; Chen, Yu Cheng; Hutchens, Shelby B.; Lawrence, Jimmy; Emrick, Todd; Crosby, Alfred J.

doi:10.1021/acs.macromol.5b01473

Cited by 109 publications

(216 citation statements)

References 47 publications

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“…The details of the set-up were described in our previous publication. [52,54,55] The molecular weight is another factor that has been observed to critically influence the mechanical property of a given polymer, which was carefully tuned to be in the similar range, as shown in Table 1. To provide a fair comparison between different DPP polymers, conjugated polymers with relatively high molecular weights were targeted and synthesized, followed by processing into thin films of similar thickness, and annealing under the same temperature and time.…”

Section: Thermomechanical Properties Of Dpp Polymersmentioning

confidence: 99%

The Critical Role of Electron‐Donating Thiophene Groups on the Mechanical and Thermal Properties of Donor–Acceptor Semiconducting Polymers

Song

Ocheje

Huang

et al. 2019

Adv Elect Materials

106

155

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Organic semiconducting donor–acceptor polymers are promising candidates for stretchable electronics owing to their mechanical compliance. However, the effect of the electron‐donating thiophene group on the thermomechanical properties of conjugated polymers has not been carefully studied. Here, thin‐film mechanical properties are investigated for diketopyrrolopyrrole (DPP)‐based conjugated polymers with varying numbers of isolated thiophene moieties and sizes of fused thiophene rings in the polymer backbone. Interestingly, it is found that these thiophene units act as an antiplasticizer, where more isolated thiophene rings or bigger fused rings result in an increased glass transition temperature (Tg) of the polymer backbone, and consequently elastic modulus of the respective DPP polymers. Detailed morphological studies suggests that all samples show similar semicrystalline morphology. This antiplasticization effect also exists in para‐azaquinodimethane‐based conjugated polymers, indicating that this can be a general trend for various conjugated polymer systems. Using the knowledge gained above, a new DPP‐based polymer with increased alkyl side chain density through attaching alky chains to the thiophene unit is engineered. The new DPP polymer demonstrates a record low Tg, and 50% lower elastic modulus than a reference polymer without side‐chain decorated on the thiophene unit. This work provides a general design rule for making low‐Tg conjugated polymers for stretchable electronics.

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Section: Thermomechanical Properties Of Dpp Polymersmentioning

confidence: 99%

The Critical Role of Electron‐Donating Thiophene Groups on the Mechanical and Thermal Properties of Donor–Acceptor Semiconducting Polymers

Song

Ocheje

Huang

et al. 2019

Adv Elect Materials

106

155

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“…Several techniques have been developed to measure the mechanical properties of ultrathin polymer films and have largely been used to elucidate deviations from bulk stiffness and residual stress . The experimental temperatures at which these studies were performed proved important in revealing different confinement behaviors below and above bulk T g : glassy softening and rubbery stiffening .…”

Section: Confined Polymer Propertiesmentioning

confidence: 99%

“…The experimental temperatures at which these studies were performed proved important in revealing different confinement behaviors below and above bulk T g : glassy softening and rubbery stiffening . Tensile testing of films supported on water and flat‐punch nanoindentation also revealed reduced elastic modulus and yield stress in confined glassy films less than ≈30 nm thick. Buckling‐based techniques on elastomer‐supported thin glassy films showed reductions in elastic modulus for both PS and PMMA upon decreasing film thickness below ≈40 nm .…”

Section: Confined Polymer Propertiesmentioning

confidence: 99%

“…As described in Section , the mechanical responses of confined polymers have also been seen to deviate substantially from bulk. Here we focus on the use of fluorescence spectroscopy to study the molecular level motion of confined polymers in response to either preparation‐induced residual stresses or externally applied stresses …”

Section: Fluorescence To Measure Mechanical Responsementioning

confidence: 99%

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21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

Burroughs

Christie

Gray

et al. 2017

Macro Chemistry & Physics

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properties. [9,10] While fluorescence has been used extensively to characterize bulk properties of polymers, including glass transition temperature (T g ) [11][12][13] and polymerization conversion, [13] it is particularly well-suited to study polymers at the nanoscale. This is largely due to the fact that fluorescence techniques enable sensitive and location-specific measurements with high resolution.In this review, we focus on the use of both steady-state and transient fluorescence techniques to characterize physical properties of polymers over nanoscale dimensions. This length scale can refer to film thickness in single-component polymer films, interparticle spacing in nanocomposites, domain spacing in phaseseparated block copolymers, and distance from the polymer-polymer interface in multicomponent immiscible blends. Several geometries characterized via fluorescence are shown in Figure 1. Prior to delving into specific contributions, the basic principles and techniques of fluorescence are presented as well as a brief introduction to the behavior of confined polymers. We then present recent advances in fluorescence techniques for polymer physical characterization under confinement with regards to the glass transition temperature, physical aging, mobility and diffusion, and mechanical response. Through this examination of the literature, we illustrate the unique ability of fluorescence to characterize polymers in confined and complex geometries, providing insights into the influences of interfaces and nanostructure on material properties through sensitive, location-specific measurements. We conclude with a view toward future areas of research in which fluorescence has the potential to be impactful. Introduction to FluorescenceWhen a molecule absorbs energy via light, an electron is excited to a higher energy state, returning to the ground state through either radiative or nonradiative deactivation. This electronic excitation and return to the ground state is a combination of three photophysical processes: absorption, luminescence, and nonradiative decay. [33] Fluorescence is a luminescent process in which the excited-state electron returns to the ground state by emitting a photon, i.e., light. As shown in a simplified Jablonski Polymer CharacterizationCharacterization of polymers at the nanometer-length scale has become increasingly important with the growth and expansion of nanotechnology. Due to limitations of sensitivity and specificity that persist with traditional materials characterization techniques, there is a growing need to develop new tools to measure the properties of confined polymer systems. Within the past 20 years, fluorescence characterization techniques have emerged to address this challenge. This review focuses on the employment of fluorescence techniques such as temperature-and time-dependent steady-state intensity, fluorescence recovery after photobleaching, and nonradiative energy transfer to study polymer behavior at the nanoscale. Properties discussed include glass transition temperatur...

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“…Measuring these properties has been difficult even for substrate-supported thin films, and there are only few measurements that have been attempted on freestanding films [11] .…”

Section: Introductionmentioning

confidence: 99%

Modeling the mechanical properties of ultra-thin polymer films

Espinosa-Loza

Stadermann

Aracne‐Ruddle

et al. 2017

High Pow Laser Sci Eng

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A modeling method to extract the mechanical properties of ultra-thin films (10-100 nm thick) from experimental data generated by indentation of freestanding circular films using a spherical indenter is presented. The relationship between the mechanical properties of the film and experimental parameters including load, and deflection are discussed in the context of a constitutive material model, test variables, and analytical approaches. Elastic and plastic regimes are identified by comparison of finite element simulation and experimental data.

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Directly Measuring the Complete Stress–Strain Response of Ultrathin Polymer Films

Cited by 109 publications

References 47 publications

The Critical Role of Electron‐Donating Thiophene Groups on the Mechanical and Thermal Properties of Donor–Acceptor Semiconducting Polymers

The Critical Role of Electron‐Donating Thiophene Groups on the Mechanical and Thermal Properties of Donor–Acceptor Semiconducting Polymers

21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

Modeling the mechanical properties of ultra-thin polymer films

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