Stretching siloxanes: An ab initio molecular dynamics study

Lupton, Elizabeth M.; Nonnenberg, Christel; Frank, Irmgard; Achenbach, Frank; Weis, Johann; Bräuchle, Christoph

doi:10.1016/j.cplett.2005.07.118

Cited by 26 publications

(48 citation statements)

References 20 publications

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“…and a fictitious electron mass of 400 a.u. In a previous study on isolated siloxanes, [17] we did not observe radical formation during bond rupture in any of the simulations. We have performed a complete simulation using the spin restricted BLYP functional [25,26] to follow the evolution of the system after rupture.…”

Section: Car-parrinello Simulations Of the Rupture Of Siloxanescontrasting

confidence: 45%

Origins of Material Failure in Siloxane Elastomers from First Principles

Lupton

Achenbach²,

Weis

et al. 2009

ChemPhysChem

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Siloxanes are versatile elastomers with an exceptional chemical and physical stability that allows them to be used as adhesives, coatings, and sealants [1] in applications ranging from biomedical to aerospace. Although these materials are exceptionally strong, they are limited by the ease of propagation of cracks through the elastomer when subjected to tensile stress. The current method of improving the material strength is to add silica filler particles, [2,3] which hinder tearing in the bulk elastomer. However, the chemical mechanism that facilitates crack propagation and the way in which the filler particles hinder it have not been defined at the molecular level. Understanding these processes entails a full description of the electronic structure of a system during the process of bond rupture and the subsequent reactions between ruptured fragments to correctly determine the underlying chemistry.Information on the response of individual chemical bonds subjected to a tensile load is accessible via single-molecule atomic force microscopy (AFM) experiments, [4][5][6] which can be interpreted with theoretical studies. [7][8][9][10][11][12][13][14][15][16][17][18][19] In the experiments, a single polymer is stretched between a substrate and an AFM tip until one of the backbone bonds ruptures. Factors that can affect the magnitude of the measured rupture force, such as the polymer length and pulling velocity, [15,17] the solvent, [16,18] the presence of knots in the polymer chain, [11,12] and the pulling of a molecule from a substrate, [13,14,19] have been examined by using Car-Parrinello molecular dynamics (CPMD) simulations. These CPMD studies provide valuable insights into the characteristics of bond rupture within single molecules, because a full electronic structure calculation is performed on the fly for a molecular dynamics trajectory, which allows a complete description of the stretching of an oligomer in the highforce regime.Of interest in understanding stress-induced material failure in the bulk elastomer is what subsequently happens to the rupture products-in particular, whether chemical reactions between the rupture products lead to permanent weakening of the material or not. Building on the results of our previous studies of the rupture of isolated siloxane oligomers, here we investigate what happens on the molecular scale when neighboring oligomers are ruptured simultaneously.CPMD simulations have previously been used to examine how rupture occurs at a knot in polyethylene chains when stretched, and how the rupture products can further react with neighboring chains to cause a tear.[20] The CÀC bonds of the backbone ruptured via a radical mechanism and then reacted with neighboring alkane chains to induce further bond rupture. Also, a disproportionation involving hydrogen transfer was observed. In our previous CPMD study of the rupture of isolated polydimethylsiloxane (PDMS) oligomers, we determined that as the siloxanes are stretched, the backbone SiÀO bonds become increasingly polarized, until rupture ...

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Section: Car-parrinello Simulations Of the Rupture Of Siloxanescontrasting

confidence: 45%

Origins of Material Failure in Siloxane Elastomers from First Principles

Lupton

Achenbach²,

Weis

et al. 2009

ChemPhysChem

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“…For example, in the force-modulation measurement 2 where a sinusoidal force signal ͑i.e., ac signal͒ of small amplitude is augmented to the constant-rate input signal and applied to drive the cantilever, the modulation frequency is limited to relatively low frequency range ͑a couple of hundreds of hertz͒ and the modulation amplitude is small ͑several tens of nanometers͒. Rapid broadband viscoelasticity measurement is needed to measure ratedependent phenomena, 3 particularly when dynamic evolution of the sample is of interest. 4 The low speed of SPM is because at high speeds, the SPM measurement of material response can suffer from large uncertainties due to the convolution of adverse effects such as hysteresis and dynamics of the piezoactuator, dynamics of the probe, the mechanical mounting, etc., into the measured data.…”

mentioning

confidence: 99%

Broadband measurement of rate-dependent viscoelasticity at nanoscale using scanning probe microscope: Poly(dimethylsiloxane) example

Kim

Zou

et al. 2008

Applied Physics Letters

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A control approach to achieve nanoscale broadband viscoelastic measurement using scanning probe microscope (SPM) is reported. Current SPM-based force measurement is too slow to measure rate-dependent phenomena, and large (temporal) measurement errors can be generated when the sample itself changes rapidly. The recently developed model-less inversion-based iterative control technique is used to eliminate the dynamics and hysteresis effects of the SPM hardware on the measurements, enabling rapid excitation and measurement of rate-dependent material properties. The approach is illustrated by the mechanical characterization of poly(dimethylsiloxane) over a broad frequency range of three orders of magnitude (∼1 Hz to 4.5 KHz).

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“…The scanning probe microscope (SPM) has become an enabling tool to quantitatively measure the mechanical properties of a wide variety of materials [2]. Current SPMbased force measurements, however, are limited by the slow operation of SPM to measure the rate-dependent phenomena of materials [3], and large measurement (temporal) errors can be generated when dynamic evolution of the material is involved during the measurement. Operating speed of current SPMs is limited by: (1) the excitation force applied, which is either quasi-static or resonant-oscillation based, is either too narrow-banded in frequency (quasi-static) or too slow (resonant oscillation based) to rapidly excite the nanomechanical behavior of materials over a broad frequency band; and (2) the hardware adverse effects can be coupled into the measured data if the measurement is at high-speed and over a broad frequency range.…”

mentioning

confidence: 99%

Control-based approach to broadband viscoelastic spectroscopy: PDMS example

Zou

Shrotriya

et al. 2009

2009 American Control Conference

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In this article, a novel nanoscale broadband viscoelastic spectroscopy approach is proposed. The proposed approach utilizes the recently developed model-less inversionbased iterative control (MIIC) technique for accurate measurement of the material response to the applied excitation force over a broad frequency band. Current nanomechanical measurement is slow and narrow-banded and thus not capable of measuring rate-dependent phenomena of materials. In the proposed approach, an input force signal with dynamic characteristics of band-limited white-noise is utilized to rapidly excite the nanomechanical response of the material over a broad frequency range. Then, the MIIC technique is used to compensate for the hardware adverse effects, thereby allowing the precise applications of such an excitation force and measurement of the material response (to the applied force). The proposed approach is illustrated by implementing it to measure the creep compliance of poly(dimethylsiloxane) (PDMS) over a broad frequency range over 3 orders of magnitude. I. INTRODUCTIONIn this article, a novel nanoscale broadband viscoelastic spectroscopy (NBVS) methodology is proposed. The proposed NBVS approach utilizes the recently developed modelless inversion-based iterative control (MIIC) technique [1] to allow rapid excitation and subsequent measurement of the nanomechanical behavior of materials over a broad frequency band. The scanning probe microscope (SPM) has become an enabling tool to quantitatively measure the mechanical properties of a wide variety of materials [2]. Current SPMbased force measurements, however, are limited by the slow operation of SPM to measure the rate-dependent phenomena of materials [3], and large measurement (temporal) errors can be generated when dynamic evolution of the material is involved during the measurement. Operating speed of current SPMs is limited by: (1) the excitation force applied, which is either quasi-static or resonant-oscillation based, is either too narrow-banded in frequency (quasi-static) or too slow (resonant oscillation based) to rapidly excite the nanomechanical behavior of materials over a broad frequency band; and (2) the hardware adverse effects can be coupled into the measured data if the measurement is at high-speed and over a broad frequency range. These adverse effects include the hysteresis of the piezo actuator (used to position the probe relative to the sample), the vibrational dynamics of the piezo actuator and the probe along with the mechanical parts, and the dynamics uncertainties.

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Stretching siloxanes: An ab initio molecular dynamics study

Cited by 26 publications

References 20 publications

Origins of Material Failure in Siloxane Elastomers from First Principles

Origins of Material Failure in Siloxane Elastomers from First Principles

Broadband measurement of rate-dependent viscoelasticity at nanoscale using scanning probe microscope: Poly(dimethylsiloxane) example

Control-based approach to broadband viscoelastic spectroscopy: PDMS example

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