Mechanical responses of a polymer graphene-sheet nano-sandwich

Li, Xiguang; Warzywoda, Juliusz; McKenna, Gregory B.

doi:10.1016/j.polymer.2014.08.008

Cited by 32 publications

(15 citation statements)

References 58 publications

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“…14,17,27,28 The data is the average for four bubbles. When the bubble deflections are larger than 3 times the film thickness-(membrane limit 29 ), the bending contribution is negligible, and the bubble is dominated by the stretching stress.…”

Section: Discussionmentioning

confidence: 99%

Ultrathin Polymer Films: Rubbery Stiffening, Fragility, and T_g Reduction

McKenna

2015

Macromolecules

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The mechanical and viscoelastic responses of poly(ethyl methacrylate) (PEMA) ultrathin films over thicknesses ranging from 21 to 112 nm have been studied using a nanobubble inflation method. The stress−strain response of the PEMA thin films shows a rubbery stiffening as the film thickness decreases, and the present results are combined with prior measurements of the rubbery stiffening index S for multiple polymers. We find that S is linearly correlated with the dynamic fragility index m. The results are also consistent with expectation from Ngai et al.'s [J. Polym. Sci., Part B: Polym. Phys. 2013, 51 (3)] recent proposition based on his coupling model but do not seem to correlate with the molecular composite concept proposed by Page et al. [Nano Lett. 2014, 14 (5)] as a means to explain the dependence of the rubbery stiffening on chemical structure of the polymer. In addition, we observe a reduction in glass transition temperature of as much as 15.7 K for PEMA films of 21 nm thickness.

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Section: Discussionmentioning

confidence: 99%

Ultrathin Polymer Films: Rubbery Stiffening, Fragility, and T_g Reduction

McKenna

2015

Macromolecules

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“…When exposed to exciting light for a long time, the luminescence intensity hardly decreases and no light flickers. , The stable fluorescence behavior of CDs can make up for the shortcomings of organic dyes and semiconductor quantum dots. At present, there are three sorts of fluorescence mechanisms proposed for CDs such as the quantum effect, surface state, and compound radiation of electron–hole pairs. , The red shift of the emission spectra that are independent of the excitation wavelength may be caused by their size, the amount of graphitic nitrogen, and emission sites. , On the contrary, CDs have a different surface state with inconformity groups because the fluorescence is dependent on the excitation wavelength . Recently, Jiang had observed that the chemical luminescence of NaIO 4 and H 2 O 2 would be enhanced by CDs due to their self-trap state .…”

Section: Introductionmentioning

confidence: 99%

Solvent Effects on Fluorescence Properties of Carbon Dots: Implications for Multicolor Imaging

Huo

Shen

et al. 2021

ACS Omega

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Carbon dots (CDs) are synthesized by the solvothermal method with four kinds of solvents including water, dimethylformamide (DMF), ethanol, and acetic acid (AA). The aqueous solutions of the above CDs emit multiple colors of blue (470 nm), green (500 nm), yellow (539 nm), and orange (595 nm). The structures, sizes, and chemical composition of the CDs are characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). The optical properties of multicolored CDs are analyzed by UV−vis absorption and photoluminescence (PL) spectra. It has been revealed that DMF is the key solvent to synthesized CDs for the red shift of fluorescence emission, which could be enhanced by adding an AA solvent. The structures of functional groups such as the contents of graphitic N in carbon cores and oxygencontaining functional groups on the surface of CDs are affected by these four solvents. According to the oxidation and selective reduction of NaBH 4 , the implication for multicolor imaging has been discussed based on the COOH, C−O−C, and CO functional groups.

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“…48,49 They also have applications in polymer fabrication, biomedicine, organic synthesis, catalysis, and sensors. [50][51][52][53][54][55][56][57] Yu et al 30 showed that the thermal conductivity of pure epoxy could be increased by 3000% by using GNPs at 25% volumetric loading. They also conducted experiments with single-walled carbon-nanotubes (SWCNTs) but found the amount of enhancement to be half of that of the GNPs.…”

Section: Introductionmentioning

confidence: 99%

Flame speed enhancement of a nitrocellulose monopropellant using graphene microstructures

Jain

Park

Chen

et al. 2016

Journal of Applied Physics

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The control and enhancement of the combustion wave propagation velocities of solid monopropellants are very important for the development of low cost and efficient micro power systems such as microthrusters and thermal-to-electrical energy conversion devices. In this work, the flame speed enhancement of a nitrocellulose (NC) solid monopropellant using highly conductive graphene structures was demonstrated. Two different graphene structures, namely, graphene foam (GF) and graphene nano-pellets (GNPs), were studied. For the GNP-doped NC films, fuel layers 500 6 30 lm thick were deposited and the doping concentrations were varied from 1% to 5% by mass. For the GF, the fuel loading ratio (%) and the foam density were varied to study their effect on the flame speed propagation behavior. Self-propagating combustion waves were observed, with average flame speed enhancements up to 8 times the bulk value. The flame speed enhancement, for both the GNPs and the GF, showed a parabolic trend as a function of their concentrations, and an optimum value for each case was determined. However, the flame speed enhancement, as a function of the GF density (for a fixed fuel loading ratio), showed a monotonic decreasing trend. Moreover, the reusability of the GF structures was also tested by re-depositing them with fuel after combustion. Similar flame speed enhancement was obtained using the fresh and the re-used GF structures.

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Mechanical responses of a polymer graphene-sheet nano-sandwich

Cited by 32 publications

References 58 publications

Ultrathin Polymer Films: Rubbery Stiffening, Fragility, and T_g Reduction

Ultrathin Polymer Films: Rubbery Stiffening, Fragility, and T_g Reduction

Solvent Effects on Fluorescence Properties of Carbon Dots: Implications for Multicolor Imaging

Flame speed enhancement of a nitrocellulose monopropellant using graphene microstructures

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Mechanical responses of a polymer graphene-sheet nano-sandwich

Cited by 32 publications

References 58 publications

Ultrathin Polymer Films: Rubbery Stiffening, Fragility, and Tg Reduction

Ultrathin Polymer Films: Rubbery Stiffening, Fragility, and Tg Reduction

Solvent Effects on Fluorescence Properties of Carbon Dots: Implications for Multicolor Imaging

Flame speed enhancement of a nitrocellulose monopropellant using graphene microstructures

Contact Info

Product

Resources

About

Ultrathin Polymer Films: Rubbery Stiffening, Fragility, and T_g Reduction

Ultrathin Polymer Films: Rubbery Stiffening, Fragility, and T_g Reduction