Partitioning of Main and Side-Chain Units between Different Phases: A Solid-State 13C NMR Inversion-Recovery Cross-Polarization Study on a Homogeneous, Metallocene-Based, Ethylene-1-Octene Copolymer

Litvinov, V. M.; Mathot, Vincent

doi:10.1006/snmr.2002.0078

Cited by 36 publications

(32 citation statements)

References 34 publications

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“…PP crystals can instead accommodate some C2 units as defects in the structure, also reducing the crystal stability and melting temperature. Our observations on the melting peak and broadening of melting range for monolayer controls are consistent with the thermal behavior of PP and PE based copolymers containing similar molar fraction of their respective comonomers …”

Section: Resultssupporting

confidence: 87%

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Mauri¹,

Ponting

Causin

et al. 2017

J Polym Sci B Polym Phys

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Shortly after processing, Polyethylene/Polypropylene (PE/PP) multilayer films demonstrate an increase in tensile modulus and other mechanical properties when the individual layer thickness is below 0.5 mm. Subsequent annealing at 60 8C for 16 h brings the properties of all other samples to similar values. WAXD characterization of the layered films identified a prevalence of mesophase in the thicker PP layers. In samples with increased layer numerosity or subjected to annealing, WAXD detected its conversion to a crystalline phase that correlates with improved mechanical properties. SSNMR and DSC detailed the defective nature of a iPP crystallites. Comonomers, detected by NMR in the commercial polymers used for the films, are the source of "tunable disorder" that dictates the formation of the PP mesophase and the low temperature of conversion to the mechanically stronger defective a phase. Soft intrafilm layer interfaces instead enable nucleation and localized polymer chain rearrangement even without annealing.

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Section: Resultssupporting

confidence: 87%

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Mauri¹,

Ponting

Causin

et al. 2017

J Polym Sci B Polym Phys

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“…For semicrystalline, high‐density polyethylene an intermediate phase could also be proven by electron microscopy 22. It appeared on both sides of the crystalline lamellae with an intermediate mobility between the amorphous and crystalline polyethylene, as seen from spin–lattice relaxation times of 13 C solid‐state NMR22–25 analysis of internal and longitudinal acoustic Raman modes,23 X‐ray diffraction,24 and discrepancies between X‐ray and DSC crystallinity 24. The size of the intermediate phase was estimated by X‐ray and 1 H spin diffusion to be about 4.0 nm for a crystalline lamellar thickness of 25–30 nm, making it a well‐defined nanophase 24.…”

Section: Resultsmentioning

confidence: 98%

Solvent Effects on Environmentally Coupled Hydrogen Tunnelling During Catalysis by Dihydrofolate Reductase from Thermotoga maritima

Loveridge

Evans

Allemann

2008

Chemistry A European J

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Protein motions may be perturbed by altering the properties of the reaction medium. Here we show that dielectric constant, but not viscosity, affects the rate of the hydride-transfer reaction catalysed by dihydrofolate reductase from Thermotoga maritima (TmDHFR), in which quantum-mechanical tunnelling has previously been shown to be driven by protein motions. Neither dielectric constant nor viscosity directly alters the kinetic isotope effect of the reaction or the mechanism of coupling of protein motions to tunnelling. Glycerol and sucrose cause a significant increase in the rate of hydride transfer, but lead to a reduction in the magnitude of the kinetic isotope effect as well as an extension of the temperature range over which "passive" protein dynamics (rather than "active" gating motions) dominate the reaction. Our results are in agreement with the proposal that non-equilibrium dynamical processes (promoting motions) drive the hydride-transfer reaction in TmDHFR.

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“…[32,33,[37][38][39][40] Although the effects of dipolar coupling are greatly reduced by motional averaging, as compared to the solid-state, line widths are still broader than those in the solution-state. The main drawback for melt-state NMR relates to the experimental conditions required to obtain fully quantitative spectra (error < 1%).…”

Section: Introductionmentioning

confidence: 99%

Optimisation and Application of Polyolefin Branch Quantification by Melt‐State ¹³C NMR Spectroscopy

Klimke

Parkinson

Piel

et al. 2006

Macro Chemistry & Physics

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Summary: Quantitative branch determination in polyolefins by melt‐state NMR has been investigated paying particular attention to sensitivity per unit time. Comparison of spectra obtained using spectrometers operating at 700, 500 and 300 MHz 1H Larmor frequency, with 4 and 7 mm MAS probeheads, showed that the best sensitivity was achieved at 500 MHz using a 7 mm 13C1H optimised high‐temperature probehead. For materials available in large quantities static melt‐state NMR, using large‐diameter detection coils at 300 MHz, was shown to produce comparable results to melt‐state MAS measurements in less time. Artificial line broadening, introduced by FID truncation, was reduced by the use of π pulse‐train heteronuclear dipolar‐decoupling. This decoupling method, when combined with a higher duty‐cycle, allowed for the whole FID to be acquired. Optimised methods have been applied to the characterisation of short‐chain branching (SCB) in polyethylene‐ and poly(propylene)‐co‐α‐olefins with varying comonomer incorporation. Long‐chain branch (LCB) concentrations of 8 branches per 100 000 CH2 were quantified for an industrial ‘linear’ polyethylene in 13 h, with a signal‐to‐noise ratio of 10 for the α branch site used. The use of J‐coupling mediated polarisation transfer techniques were also shown to be viable for branch quantification in the melt‐state.An example of the time efficient quantification of very low branch contents in polyethylene using optimised 13C melt‐state NMR under magic‐angle spinning. Concentrations of 7–8 branches per 100 000 CH2 groups were determined in only 13 h.magnified imageAn example of the time efficient quantification of very low branch contents in polyethylene using optimised 13C melt‐state NMR under magic‐angle spinning. Concentrations of 7–8 branches per 100 000 CH2 groups were determined in only 13 h.

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Partitioning of Main and Side-Chain Units between Different Phases: A Solid-State 13C NMR Inversion-Recovery Cross-Polarization Study on a Homogeneous, Metallocene-Based, Ethylene-1-Octene Copolymer

Cited by 36 publications

References 34 publications

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Solvent Effects on Environmentally Coupled Hydrogen Tunnelling During Catalysis by Dihydrofolate Reductase from Thermotoga maritima

Optimisation and Application of Polyolefin Branch Quantification by Melt‐State ¹³C NMR Spectroscopy

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Partitioning of Main and Side-Chain Units between Different Phases: A Solid-State 13C NMR Inversion-Recovery Cross-Polarization Study on a Homogeneous, Metallocene-Based, Ethylene-1-Octene Copolymer

Cited by 36 publications

References 34 publications

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Solvent Effects on Environmentally Coupled Hydrogen Tunnelling During Catalysis by Dihydrofolate Reductase from Thermotoga maritima

Optimisation and Application of Polyolefin Branch Quantification by Melt‐State 13C NMR Spectroscopy

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Optimisation and Application of Polyolefin Branch Quantification by Melt‐State ¹³C NMR Spectroscopy