Proton residual dipolar couplings by NMR magnetization exchange in cross-linked elastomers: determination and imaging

Gasper, L.; Demco, Dan E.; Blümich, Bernhard

doi:10.1016/s0926-2040(99)00012-0

Cited by 9 publications

(7 citation statements)

References 28 publications

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“…In the limit of experimental errors these ratios show a linear dependence. This linear dependence underlines again the validity of the simple model employed for evaluating residual dipolar couplings (15) which has been used previously in studies of polybutadiene (3,16,17) and synthetic 1,4-cispolyisoprene (4). However, the lines in Fig.…”

Section: Resultssupporting

confidence: 66%

Double-Quantum-Filtered NMR Signals in Inhomogeneous Magnetic Fields

Wiesmath

Filip

Demco

et al. 2001

Journal of Magnetic Resonance

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Section: Resultssupporting

confidence: 66%

Double-Quantum-Filtered NMR Signals in Inhomogeneous Magnetic Fields

Wiesmath

Filip

Demco

et al. 2001

Journal of Magnetic Resonance

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“…The network dynamics may be apparent in the data presented here, but it is more likely that these are masked by decoherence effects caused by higher-order spin interactions . We propose to investigate these effects in future work, in particular by applying a new version of the β rf pulse sequence which more effectively refocuses dephasing caused by multiple spin interaction terms in the dipolar Hamiltonian.…”

Section: Discussionmentioning

confidence: 97%

Molecular Weight Dependence of Nuclear Spin Correlations in PDMS Networks

Callaghan

Samulski

2000

Macromolecules

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We present experimental proton NMR data for poly(dimethylsiloxane) (PDMS) model networks in the form of a β-echo (sine correlation) function which is particularly sensitive to modulations of nuclear dipolar interactions caused by slow molecular reorientations. The β-echo can be computed with a correlation function which allows for preaveraging of local dipolar interactionssmethyl group rotation, intra-Kuhn-segment isomerization, extra-segment reorientations due to (restricted) Rouse modes, and slower modulations due to network fluctuationssto yield a residual proton second moment, M 2 . The data were obtained from networks with inter-cross-link molar mass, MX, covering a wide range both below and above the entanglement mass, Me. Fits of the β-echo give quite reliable estimates of the preaveraged dipolar interaction strength M 2 , and these indicate a clear dependence on MX, in which the role of physical entanglements is dramatically evident. Network dynamics cannot be reliably ascertained due to the effect of higher-order spin interactions.

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“…-increases of relaxation times T 1 and T 2 when temperature (and mobility) increases [30], -increases of stretched exponential relaxation times for elastomers with various crosslinking degrees at a fixed temperature [31].…”

Section: Possible Initial Architecture Of Networkmentioning

confidence: 99%

Plasticizer effect on network structure and hydrolytic degradation

Richaud

Derue

Pierre

et al. 2015

European Polymer Journal

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a b s t r a c tThe hydrolytic degradation of fully cured polyester-urethane networks polymerized in the presence of several weight ratios of triacetin was monitored by the residual concentration in elastically active chains obtained from modulus and equilibrium solvent swelling measurements. The presence of triacetin does not change the water uptake but induces a lower rate of degradation. Comparisons were performed with networks in which triacetin was removed before ageing, and with networks in which polyester-urethane was first polymerized and then impregnated by triacetin. Data suggest that the presence of triacetin during polymerization induces the presence of elastically inactive chains such as dangling chains and loops, the hydrolysis of which does not change the elastic properties of the network. This explanation was checked from relaxation measurements by NMR and DMA, and by the analysis of the soluble fraction generated by hydrolysis.

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Proton residual dipolar couplings by NMR magnetization exchange in cross-linked elastomers: determination and imaging

Cited by 9 publications

References 28 publications

Double-Quantum-Filtered NMR Signals in Inhomogeneous Magnetic Fields

Double-Quantum-Filtered NMR Signals in Inhomogeneous Magnetic Fields

Molecular Weight Dependence of Nuclear Spin Correlations in PDMS Networks

Plasticizer effect on network structure and hydrolytic degradation

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