RADIATION CHEMISTRY OF HEXAMETHYLDISILOXANE, A POLYDIMETHYLSILOXANE MODEL<sup>1</sup>

Dewhurst, H. A.; Pierre, L. E. St.

doi:10.1021/j100837a025

Cited by 30 publications

(14 citation statements)

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“…Silanols are known to form in irradiated PDMS in the presence of large concentrations of strong hydrogen donors such as alkylthiols . Small quantities of silanol products were found in hexamethyldisiloxane irradiated under an inert N 2 atmosphere . Water is a common environmental antagonist known to be coupled to silanol production.…”

Section: Insights From Qm Modelingmentioning

confidence: 99%

“…56 Small quantities of silanol products were found in hexamethyldisiloxane irradiated under an inert N 2 atmosphere. 74 Water is a common environmental antagonist known to be coupled to silanol production. Experimental NMR measurements found that thermal and radiative aging of PDMS in the presence of 17 O-labled water led to 17 O uptake in silanol groups and the main chain.…”

Section: ■ Insights From Qm Modelingmentioning

confidence: 99%

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Constitutive Model of Radiation Aging Effects in Filled Silicone Elastomers under Strain

et al. 2021

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Filled silicone elastomers, an essential component in many technological applications, are often subjected to controlled or unintended radiation for a variety of reasons. Radiation exposure can lead to permanent mechanical and structural changes in the material, which is manifested as altered mechanical response, and in some cases, a permanent set. For unfilled elastomers, network theories developed and refined over decades can explain these effects in terms of chain-scission and cross-link formation and a hypothesis involving independent networks formed at different strain levels of the material. Here, we expose a filled silicone rubber to gamma radiation while being under finite elongational strain and show that the observed mechanical and structural changes can be quantitatively modeled within the same theoretical framework developed for unfilled elastomers as long as nuances associated with the Mullins effect are accounted for in a consistent manner. In this work, we employ Ogden's incompressible hyperelastic model within the framework of Tobolsky's two-network scheme to describe the observed permanent set and mechanical modulus changes as a function of radiation dosage. In the process, we conclude that gamma radiation induces both direct cross-linking at chain crossings (H-links) and main-chain-scission followed by cross-linking (Y-links). We provide an estimate of the ratio of chain-scission to crosslinking rates, which is in reasonable agreement with previous experimental estimate from Charlesby−Pinner analysis. We use density functional theory (DFT)-based quantum mechanical calculations to explore the stability of −Si and −SiO radicals that form upon a radiation-induced chain-scission event, which sheds light on the relative rates of Y-linking and H-linking processes.

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Section: Insights From Qm Modelingmentioning

confidence: 99%

Section: ■ Insights From Qm Modelingmentioning

confidence: 99%

Constitutive Model of Radiation Aging Effects in Filled Silicone Elastomers under Strain

et al. 2021

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“…Quantitative trends among the experiments are difficult to discern. Results from Zack et al 66 Significant spread is seen for relative CH 4 production despite similar radiation sources and inert N 2 atmosphere, as seen by comparing the experiments of St. Pierre et al, 67 Dewhurst and St. Pierre, 22 and Miller. 21 Perhaps interestingly, those experiments show similar relative production of C 2 H 6 .…”

Section: Time-dependent Small Molecule Productionmentioning

confidence: 86%

“…We also determine no difference between exciting Me-H or H Experimental measurements of small molecule off-gassing were made in a number of independent studies that considered different radiation sources and PDMS molecular weights. [20][21][22]64,[66][67][68] Relative concentrations of H 2 , CH 4 , and C 2 H 6 referenced to the H 2 concentration [H 2 ] measured in these experiments are collected in Table 2, along with information on the form of the PDMS material sample, the radiation source (reactor piles, 60 Co γ-rays, or high-energy electrons e − ), and headspace gases exposed to the sample (if known). These are compared to analogous values predicted here from QMD, which correspond to the ensembleaverage results at time t = 21 ps in Figure 5.…”

Section: Time-dependent Small Molecule Productionmentioning

confidence: 99%

“…[4][5][6][7][8][9][10][11][12]16,17 Ionizing radiation is a common cause for polymer degradation that can arise during component sterilization, 1,18,19 as a consequence of planned operation conditions, and as a driver in accelerated aging studies. [7][8][9][10][11][12] In 1955, Charlesby proposed 20 a set of reaction schemes for crosslinking in irradiated PDMS that were quickly refined by others 21,22 and were based on IR vibrational spectroscopy, titration, mass spectra of off-gassing species, and chromatography (see Figure 1). These reactions respectively connect the evolution of hydrogen (H 2 ), methane (CH 4 ), and ethane (C 2 H 6 ) with the formation of silethylene (Si-C-C-Si), silmethylene (Si-C-Si), and silicon-silicon (Si-Si) crosslinks.…”

Section: Introductionmentioning

confidence: 99%

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Polymer Degradation through Chemical Change: A Quantum-based Test of Inferred Reactions in Irradiated Polydimethylsiloxane

Kroonblawd

Goldman

Maiti

et al. 2021

Preprint

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Chemical reaction schemes are key conceptual tools for interpreting the results of experiments and simulations, but often carry implicit assumptions that remain largely unverified for complicated systems. Established schemes for chemical damage through crosslinking in irradiated silicone polymers comprised of polydimethylsiloxane (PDMS) date to the 1950's and correlate small-molecule off-gassing with specific crosslink features. In this regard, we use a somewhat reductionist model to develop a general conditional probability and correlation analysis approach that tests these types of causal connections between proposed experimental observables to reexamine this chemistry through quantum-based molecular dynamics (QMD) simulations. Analysis of the QMD simulations suggests that the established reaction schemes are qualitatively reasonable, but lack strong causal connections under a broad set of conditions that would enable making direct quantitative connections between off-gassing and crosslinking. Further assessment of the QMD data uncovers a strong (but nonideal) quantitative connection between exceptionally hard-to-measure chain scission events and the formation of silanol (Si-OH) groups. Our analysis indicates that conventional notions of radiation damage to PDMS should be further qualified and not necessarily used ad hoc. In addition, our efforts enable independent quantum-based tests that can inform confidence in assumed connections between experimental observables without the burden of fully elucidating entire reaction networks.

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Effet De La Temperature Sur Les Rendements Des Produits Lourds Dans La Radiolyse Be L'hexane Normal Par Des Electrons Acceleres

Fontaine

Tilquin²,

Claes³

1975

Bulletin des Soc Chimique

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RADIATION CHEMISTRY OF HEXAMETHYLDISILOXANE, A POLYDIMETHYLSILOXANE MODEL¹

Cited by 30 publications

References 0 publications

Constitutive Model of Radiation Aging Effects in Filled Silicone Elastomers under Strain

Constitutive Model of Radiation Aging Effects in Filled Silicone Elastomers under Strain

Polymer Degradation through Chemical Change: A Quantum-based Test of Inferred Reactions in Irradiated Polydimethylsiloxane

Effet De La Temperature Sur Les Rendements Des Produits Lourds Dans La Radiolyse Be L'hexane Normal Par Des Electrons Acceleres

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RADIATION CHEMISTRY OF HEXAMETHYLDISILOXANE, A POLYDIMETHYLSILOXANE MODEL1

Cited by 30 publications

References 0 publications

Constitutive Model of Radiation Aging Effects in Filled Silicone Elastomers under Strain

Constitutive Model of Radiation Aging Effects in Filled Silicone Elastomers under Strain

Polymer Degradation through Chemical Change: A Quantum-based Test of Inferred Reactions in Irradiated Polydimethylsiloxane

Effet De La Temperature Sur Les Rendements Des Produits Lourds Dans La Radiolyse Be L'hexane Normal Par Des Electrons Acceleres

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RADIATION CHEMISTRY OF HEXAMETHYLDISILOXANE, A POLYDIMETHYLSILOXANE MODEL¹