NMR studies of the radiation modification of polymers

Hill, David J. T.; Whittaker, Andrew K.

doi:10.1016/s0066-4103(02)46016-4

Cited by 9 publications

(5 citation statements)

References 125 publications

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“…Nuclear magnetic resonance (NMR) spectroscopy has played a substantial role in enhancing comprehension of the ramifications of radiation on polymeric systems 62 .The significance of NMR as a methodology is underscored by its capacity to enable the precise attribution of signals to individual atoms within both the polymer’s main chain and its side chains 63 – 65 . The 1 H-NMR spectra of commercially studied EVA are presented in Fig.…”

Section: Resultsmentioning

confidence: 99%

Gamma radiation-induced grafting of poly(butyl acrylate) onto ethylene vinyl acetate copolymer for improved crude oil flowability

Siddiq,

Ghobashy,

El-Adasy

et al. 2024

Sci Rep

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Ethylene vinyl acetate (EVA) copolymers are widely employed as pour point depressants to enhance the flow properties of crude oil. However, EVA copolymers have limitations that necessitate their development. This work investigated the modification of EVA via gamma radiation-induced grafting of butyl acrylate (BuA) monomers and the evaluation of grafted EVA as a pour point depressant for crude oil. The successful grafting of poly(butyl acrylate) p(BuA) onto EVA was verified through grafting parameters, FTIR spectroscopy, and 1H NMR spectroscopy. Treating crude oil with 3000 ppm of (EVA)0kGy, (EVA)50kGy, and (1EVA:3BuA)50kGy yielded substantial reductions in pour point of 24, 21, and 21 °C, respectively. Also, rheological characterization demonstrated improving evidenced by a viscosity reduction of 76.20%, 67.70%, and 71.94% at 25 °C, and 83.16%, 74.98%, and 81.53% at 12 °C. At low dosages of 1000 ppm, the EVA-g-p(BuA) exhibited superior pour point reductions compared to unmodified EVA, highlighting the benefit of incorporating p(BuA) side chains. The grafted EVA copolymers with p(BuA) side chains showed excellent potential as crude oil flow improvers by promoting more effective adsorption and co-crystallization with paraffin wax molecules.

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Section: Resultsmentioning

confidence: 99%

Gamma radiation-induced grafting of poly(butyl acrylate) onto ethylene vinyl acetate copolymer for improved crude oil flowability

Siddiq,

Ghobashy,

El-Adasy

et al. 2024

Sci Rep

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“…NMR spectroscopy is regarded as the most informative analytical tool in polymer science, and has been applied to the study of the radiation chemistry of polymers over many years. 36 To generate sufficient sample for the 19 F solution-state NMR spectra reported here approximately with a 157 nm laser to a dose of 20 J cm -2 are presented in Figure 8. In this region of the spectrum, the HFB solvent has three peaks due to impurities which have been marked with asterisks.…”

Section: Resultsmentioning

confidence: 99%

“…Analysis of Bulk Chemistry. NMR spectroscopy is regarded as the most informative analytical tool in polymer science, and has been applied to the study of the radiation chemistry of polymers over many years . To generate sufficient sample for the 19 F solution-state NMR spectra reported here approximately 20 thin films (4 cm 2 area, ∼1 μm thick) were each irradiated to a dose of 20 J cm -2 .…”

Section: Resultsmentioning

confidence: 99%

Mechanism of 157 nm Photodegradation of Poly[4,5-difluoro-2,2- bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene] (Teflon AF)

et al. 2007

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The photodegradation at 157 nm of thin films of a series of Teflon AF copolymers has been comprehensively examined using electron spin resonance, NMR, FTIR, and Raman spectroscopies, mass spectrometry and X-ray photoelectron spectroscopy. The mechanism of degradation involves reaction at the dioxole units, and as a consequence the sensitivity to degradation increases across the series Teflon AF 1200, 1600, and 2400. A major volatile product is hexafluoroacetone formed by degradation at the dioxole unit. NMR and volatile product analysis confirm that degradation occurs largely at the dioxole unit leading to an array of new chain-end species. Main-chain and chain-end carbon-centered radicals were identified as arising from abstraction reactions and main-chain cleavage, respectively. In addition to loss of the dioxole units, XPS analysis indicates extensive char formation at the film surface, providing evidence of loss of fluorine atoms which in turn may react with free radical intermediates to form stable products identified by NMR. The implications for design of materials for 157 nm photolithography are discussed.

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“…The published works of Lyons and Sheirs includes a detailed discussed on the radiation chemistry of FEP in the presence and absence of oxygen at various doses and dose rates (26, 27). The radiolytic chemical structures and the radiation chemical yields (G values) of irradiated FEP have been reviewed elsewhere (28, 29). Radiolysis of FEP yields various types of C-centered radicals.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms and Characterization of the Pulsed Electron-Induced Grafting of Styrene onto Poly(tetrafluoroethylene-co-hexafluoropropylene) to Prepare a Polymer Electrolyte Membrane

et al. 2018

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During the pulsed-electron beam direct grafting of neat styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) substrate, the radiolytically-produced styryl and carbon-centered FEP radicals undergo various desired and undesired competing reactions. In this study, a high-dose rate is used to impede the undesired free radical homopolymerization of styrene and ensure uniform covalent grafting through 125-μm FEP films. This outweighs the enhancement of the undesired crosslinking reactions of carbon-centered FEP radicals and the dimerization of the styryl radicals. The degree of uniform grafting through 125-μm FEP films increases from ≈8%, immediately after pulsed electron irradiation to 33% with the subsequent thermal treatment exceeding the glass transition temperature of FEP of 39°C. On the contrary, steady-state radiolysis using Co gamma radiolysis, shows that the undesired homopolymerization of the styrene has become the predominant reaction with a negligible degree of grafting. Time-resolved fast kinetic measurements on pulsed neat styrene show that the styryl radicals undergo fast decays via propagation homopolymerization and termination reactions at an observed reaction rate constant of 5 × 10 l · mol · s. The proton conductivity of 25-μm film at 80°C is 0.29 ± 0.01 s cm and 0.007 s cm at relative humidity of 92% and 28%, respectively. The aims of this work are: 1. electrolyte membranes are prepared via grafting initiated by a pulsed electron beam; 2. postirradiation heat-treated membranes are uniformly grafted, ideal for industry; 3. High dose rate is the primary parameter to promote the desired reactions; 4. measurement of kinetics of undesired radiation-induced styrene homopolymerization; and 5. The conductivity of prepared membranes is on par or higher than industry standards.

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NMR studies of the radiation modification of polymers

Cited by 9 publications

References 125 publications

Gamma radiation-induced grafting of poly(butyl acrylate) onto ethylene vinyl acetate copolymer for improved crude oil flowability

Gamma radiation-induced grafting of poly(butyl acrylate) onto ethylene vinyl acetate copolymer for improved crude oil flowability

Mechanism of 157 nm Photodegradation of Poly[4,5-difluoro-2,2- bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene] (Teflon AF)

Mechanisms and Characterization of the Pulsed Electron-Induced Grafting of Styrene onto Poly(tetrafluoroethylene-co-hexafluoropropylene) to Prepare a Polymer Electrolyte Membrane

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