NMR of elastomers and biological tissues

An important objective of polymer science is to establish relationships between the microscopic structure or molecular dynamics and the macroscopic properties of materials. Once established, this knowledge then allows the design polymers with improved properties. A new method called AIMS (Accordion Magic Sandwich), which scan the dipolar magic echo shape with the Hahn echo, was developed. Using this method the residual second and fourth van Vleek moments, which are more sensitive to cross-link density, were measured, model free, without the interference originated from static and radiofrequency magnetic fields, or local susceptibility. The mixed echo decays, which are characterized by 1H residual second van Vleck moment, multispin dipolar correlation time or parameters of the correlation time distribution, were measured for a series of natural rubber samples with different cross-link densities. The measured segmental order was shown to scale with a polynomial dependence on cross-link density or shear modulus. A Maxwell-Boltzmann type of the distribution function of the end-to-end vector can characterized better the orientation of the polymer chains into a polymer network. The effect of stress and orientation of the stressed elastomers in static magnetic fields on the proton second van Vleek moment was studied using the mixed echo and multipolar spin states. Theoretically and experimental was demonstrates the possibility to obtain an enhanced sensitivity to the change in the values of residual dipolar couplings by measuring high order multiple quantum coherences. By an ingenious combination of high resolution magic angle sample spinning with the 2D double-quantum filtered spectroscopy and the chemical shift filter the magnetisation exchange process between different functional groups was evidentiated and characterized. The measurement of the self-diffusion coefficient of small penetrant molecules was used as a new tool to determine the polymer networks deformation under stress or compression. The global anisotropy of the collagen fibril orientation in Achilles tendon, evidentiated in the measurement of 1H residual dipolar couplings determined from DQ build-up curves and DQ-filtered doublets as well as dipolar encoded longitudinal magnetisation of bounded water interacting with the collagen fibers, was investigated quantitatively, using a Gaussian distribution functions, and a expansion in Legendre polynomials distribution function. Moreover a localized anisotropy was measured using 1H NMR images of tendons under mechanical load conditions encoded by the residual dipolar couplings of bound water. Two mobile NMR sensors and a series of radiofrequency coils were characterized. For the simulations of the NMR spine system response in the inhomogeneous magnetic field a simulation program was written in C++. The sensitive volumes of two NMR mobile sensors were studied for different experimental condition like the operating frequency and different RF pulses sequences. The 1H self-diffusion coefficients of mobile molecules in complex protonated system with a strong restriction in their mobility were measured using the constant relaxation method.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Fechete, Radu

Contributors dc:contributor

• Blümich, Bernhard

• info:eu-repo/classification/ddc/540
• Elastomer
• NMR-Spektroskopie
• Hochauflösendes Verfahren
• Achillessehne
• Kollagene Faser
• Chemie
• NMR
• elastomers
• ordered tissues
• MOUSE

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121060%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59257