Advanced NMR analysis of polymers and biomolecules

The importance of one of the matter-investigation methods can be quantified by considering the number of Nobel awards given to a specific domain in science. Nuclear magnetic resonance has thirteen Nobel awards, the last three ones being given in the last twenty years. Over the years NMR undertook many applications, becoming one of the most versatile, non-invasive methods for investigating various states of matter. It is now a common research tool in solid state chemistry and condensed matter physics and one of the few methods available for determining the structures of proteins and nucleic acids in their native solution state. It expanded also into medicine, both as an imaging, as well as a spectroscopy tool to study metabolism, diagnose malignancy, angiograph non-invasively, and reveal brain function. The present work reports the results obtained by NMR spectroscopy and relaxometry on advanced polymers like ultra-high molecular weight polyethylene (UHMWPE), diblock copolymers, isotactic polypropylene / silica nanocomposite, porous polypropylene, and elastomers. Also, the dynamic behaviour of lecithin in bulk and in geometrically confined states, and the morphological and molecular dynamics changes induced by hydration of hard α-keratin were investigated. Several new NMR methods were developed and applied to investigate advanced materials. For instance, multidimensional ultrafast spectroscopy was developed for the first time for solids under magic angle sample spinning (MAS) conditions. The rotor-synchronized stimulated echo method is introduced as a new tool for the characterization of polymer chain dynamics. A modern procedure for interpreting proton spin-diffusion experiments for different polymer morphologies is also discussed. The chemical site-specific dynamics of lecithin using 13C spectroscopy, 1H-13C wideline separation (WISE), 1H-13C rotational echo double resonance (REDOR), spin-lattice relaxation in the rotating frame, 31P wideline spectroscopy, and thermally polarized 129Xe has been investigated. Such a study using a combination of different advanced NMR methods was never reported before. A coherent picture that correlates the chemical sites and molecular dynamics resulted from this investigation. For the first time the correlation between the quantitative morphology and the chain dynamics of polymethylmethacrylate-co-polystyrene (PMMA-co-PS) diblock copolymer was established. The domain sizes of each block were measured by 1H spin-diffusion. The chain dynamics was investigated by 13C spin-lattice relaxation time in the rotating frame. The possibility to use a spectroscopic NMR method in combination with relaxometry was also discussed in this work. The time evolution of the 1H spectra edited by the stimulated echo for a rotor synchronized pulse sequence was used for measuring site-selective residual dipolar couplings in cross-linked natural rubber. A theoretical description of this method based on the evolution of the density operator was developed for an arbitrary value of the pulse flip angle. The method allows fast NMR experiments, using the Ernst-angle approach. This is of great importance for the investigation of large series of elastomers samples differing in cross-link density and filler content. One of the chapters of this work is related to the investigation of phase composition, chain dynamics and domain sizes for isotactic polypropylene (iPP) with silicon oxide nanoparticles. NMR spectroscopy of 1H and 29Si was used to study the SiO2 network obtained by in situ conversion of polyethoxysiloxanes (PEOS) under various experimental conditions. The iPP/SiO2 nanocomposites, obtained by blending iPP with PEOS in different weight percentages, was characterized by 1H wideline spectroscopy and 1H spin-diffusion. The structural information was corroborated with mechanical and thermal properties. Moreover, these data are in agreement with SAXS and WAXS results. The structure – property relationship was investigated for a series of experimental UHMWPE Dyneema® fibers with different tensile strengths. Proton wideline spectra under static and fast MAS (10 kHz), 1H spin-diffusion, 13C spectroscopy, 13C-1H WISE, and T1 edited 13C spectra were used to characterize the changes in morphology and chain dynamics with the fibers drawing. Such a detailed investigation was performed for the first time on these materials. Moreover, the existence of an intermediate fraction was detected and its properties investigated. The voids induced in the process of fibers drawing were characterized with spectra of thermal polarized 129Xe. The new method of ultrafast multidimensional NMR spectroscopy proposed by Prof. Frydman was extended to the field of solids under MAS. It is expected for this new tool to find new applications especially for the study of dynamic processes. The possibility to apply exchange spectroscopy under ultrafast 2D conditions was explored for LASER-hyperpolarized 129Xe in porous polymer membranes. The morphological and molecular dynamics changes induced by hydration of hard alpha-keratin are evaluated. The fraction composition and side-chain dynamics were measured on Caucasian hair at different levels of hydration by 1H wide-line spectra. The rigid and mobile domain sizes were determined by 1H spin-diffusion using the initial-rate approximation in combination with the quasi-equilibrium ratio of the NMR signals.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2009

Author dc:creator

• Melian-Flamand, Claudiu

Contributors dc:contributor

• Blümich, Bernhard

• info:eu-repo/classification/ddc/500
• Mehrdimensionale NMR-Spektroskopie
• Nanokomposit
• Diblockcopolymere
• Lecithin-Cholesterin-Acyltransferase
• Keratine
• Xenon-129
• PE-UHMW
• Naturwissenschaften
• Hyperpolarisierte 129Xe NMR
• schnelle Mehrdimensionale NMR-Spektroskopie
• fast NMR spectroscopy
• drawn UHMWPE fibers
• PP/silica nanocomposites
• keratin
• hyperpolarized 129Xe NMR

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113596%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A51289