"Water, Water, Everywhere" begins a famous quatrain by the English poet Samuel Taylor Coleridge. Indeed, there is no chemical compound more ubiquitous or more crucial to all aspects of life on Earth. Most familiar is water in its liquid form, a material that is a near-universal solvent. Sea water, a solution of inorganic salts in water, represents more than 95% of the water on the surface of the planet. While water molecules are essential to life, many aspects of their involvement in biological structures and processes are not fully understood.
Formed from a single oxygen atom and two hydrogens, the physical and chemical properties of water are often anomalous if the hydrogen compounds of the elements surrounding oxygen in the periodic table are considered. For example, water (H2O) is a liquid at room temperature and atmospheric pressure while the compounds NH3, HF and H2S are gases under the same conditions. The anomalous properties of water result from intermolecular dipolar and hydrogen-bonded interactions that are peculiarly potent in pure water and account for this liquid's ability to function so effectively as a solvent. The same types of interactions often lead to water molecules being found within organized three-dimensional structures of living and inanimate materials where they have specific structural roles that go beyond those of a mere solvent.
Many experimental methods have been applied to the study of water as a solvent or as a part of an assembled structure. Given that water contains hydrogen atoms with their spin ½ nuclei, it is no surprise that proton nuclear magnetic resonance (1H NMR) has been at the forefront of efforts to understand the chemistry of water wherever it is found. Proton NMR can provide information about the stability of organized structures and indications of the time rate(s) of change of these. Such changes might include rearrangement of three-dimensional aspects (such as conformational motions) or change in relative positions through rotational and translational diffusion.
In this volume, Dr. Rodin presents results from his laboratory and those of others that exemplify information that can be obtained about water molecules contained within organized but non-crystalline materials using proton NMR. These efforts appropriately have employed various relaxation, multiple quantum filtered, translational diffusion and imaging experiments. The systems examined range from synthetic (polyacrylates) and natural polymers (collagen and silk) to intact wood and inorganic cements. These reports nicely demonstrate to the reader the current state of the art in applying these powerful NMR experiments to the systems mentioned.
J. T. Gerig, Professor Emeritus
University of California
Nuclear Magnetic Resonance (NMR) is an indispensable technique for investigating the structure, functionality and dynamics of molecules. It is used widely in physics, chemistry, biology, medicine and other sciences. In this book, Dr. Victor Rodin describes NMR experiments and techniques for consideration and discussion. This book is a great addition to the analysis of NMR methods which Dr. Victor Rodin applied in studying the translational dynamics of molecules in porous and heterogeneous systems: synthetic polymers and materials, collagens and natural silk, and wood and cement pastes.
Dr. Rodin graduated from the Moscow Institute of Physics and Technology (MIPT-State University), Faculty of Molecular & Chemical Physics. He received a PhD in Biophysics (with specialization in Mathematics & Physics) at the Research Institute of Biophysics (Russian Academy of Sciences). He also earned a PhD in Macromolecular and Colloid Chemistry at the Department of Chemistry of Moscow State University. He has worked in excellent NMR research centers, including the University of California, Santa Barbara, USA; the University of East Anglia; the University of Bristol; the University of Surrey, UK; INRA, Clermont-Ferrand, France; Johannes Kepler University of Linz, Austria. Dr. Rodin has published more than 60 publications in peer-reviewed scientific journals and delivered approximately 70 presentations at international scientific meetings and conferences. He has been a member of the Research Council on Colloid Chemistry at Moscow State University, and a member of the International Society of Magnetic Resonance in Medicine, USA. He has refereed papers for scientific journals including Colloid Journal, Material Science, Polymer, Food Chemistry, and a special issue of Magnetic Resonance in Porous Media.
Dr. Rodin has considerable experience in the development of different magnetic resonance methods, including new methodologies. His research experience focuses on the development and application of MR methods and analysis to study solutions and heterogeneous materials, including biomaterials and drugs, blood and microbiological suspensions, polymer solutions, gels and films, xenon gas clathrate hydrates, collagen tissues, natural silk, skin, wood, cement etc. He has taught in many universities. Based on his research results he has delivered lectures to students in physics, physical chemistry, mathematics, natural biopolymers and synthetic materials.
Dr. Rodin illustrates the current state of numerous special NMR experiments applied to porous heterogeneous materials. Readers with an interest in NMR will find useful information in this volume. Potential roles of NMR to future applications are also discussed. The examples are taken from real research results. Problems and solutions are also considered.
Syed F. Akber, PhD, DABR
Cleveland/ Lorain, OHIO
NMR has been used extensively to estimate the amount of water as well as water self-diffusion in porous natural as well as man-made polymeric materials. It is well known that water is not simply a medium in which biomolecules happen to exist, interact and carry out their functions. Almost every aspect of biomolecular chemistry and physics is influenced by the properties of the liquid milieu. The changes in hydration dynamics of biomolecules upon interaction with other molecules are critical for its functional applications such as for tissue engineering. The author himself is very well versed in understanding hydration dynamics of macromolecules especially silk and collagen, the widely used biomaterials in tissue engineering. Dr. V.V. Rodin’s experience in understanding water diffusivity with other polymeric materials viz., wood and acrylic polymers is also immense. Materials used in cement industry are within his research as well.
The book starts with the basic understanding of NMR principles and concentrates on the description of NMR relaxation and diffusion experiments to understand dynamic properties of bound water in natural polymers and explains in detail the theory behind how such experiments work. The 2D diffusion-diffusion correlation NMR spectroscopy needed to study diffusion anisotropy in wood is introduced step by step, with the emphasis on obtaining a good understanding of how the experiments actually work. Water-polymer interactions and self-diffusion of water in polymer films studied using NMR are also detailed vividly.
Biophysicists and polymer chemists who read this book will be rewarded with fundamental understanding of number of NMR methodologies in studying different heterogeneous materials at a level that will allow them to make use of this versatile spectroscopic method for investigating water dynamics of natural proteins, synthetic polymers and other porous heterogeneous materials.
N. Nishad Fathima
Principal Scientist, PhD
CSIR-Central Leather Research Institute
This is a book about studies of water motion by the author and his collaborators for a number of natural polymers, such as wood and silk, for the synthetic polymers, and for some cement pastes. Various advanced NMR relaxation and diffusion measurements were performed. These include T1-T2 cross correlation relaxation and diffusion-diffusion correlation spectroscopy with parallel and perpendicular pulsed field gradients. A measurement of self diffusion of a polymer itself is also made.
Victor Rodin, working in magnetic resonance methods at the University of Linz, at Linz, Austria, has had a life long professional interest in the physical properties of natural and synthetic polymers, including collagen, wood, and mineral type materials, especially in regard to the static and dynamic properties of water associated with these materials. Studies have also included water bound in clathrates.
Dr. Rodin has authored or co-authored over 60 articles in English and Russian journals, including a chapter in the 2017 Encyclopedia of Physical Organic Chemistry.
Hopefully, readers with different backgrounds in physics, chemistry, and biology will acquire much useful information from these studies of water-macromolecule and pore-water interactions in organized structures. Not only is the information about the systems themselves of value; but the methods used to acquire the information can be applied to many other systems.
John E. Tanner, Jr., PhD
This book presents an analysis of those nuclear magnetic resonance (NMR) methods which are used in the studying translational dynamics of molecules in different complex systems including synthetic and natural polymers, tissues, and the porous heterogeneous systems of different destination. The results of proton spin-lattice and spin-spin relaxation, cross-relaxation, pulse field gradient (PFG) NMR in studying diffusion properties and dynamics of molecules in polymer systems of different complexity are reported: from polymer solutions to polymer films and biomaterials of natural origin. The book describes a number of NMR methodologies in studying different heterogeneous materials. In addition to these methods, double-quantum-filtered (DQF) NMR technique in a study of slow molecular dynamics and properties of the systems with the anisotropic properties is presented. DQF NMR is working in investigating the systems, in which there is an order. It is effectively applied in the systems with anisotropic motion of molecules. The examples are presented on natural silk, collagens, and materials of construction destination. It is considered also how DQF NMR spectroscopy highlights water in hardening cement pastes.
The apparent translational diffusion coefficients (Dapp) at two orthogonal directions of applied gradient in oriented fibers of natural polymers/materials were studied and discussed to clarify diffusion and estimate the restricted distance and permeability. The book considered the results of the approaches of one-dimensional and two-dimensional NMR and showed how these methods work in addition to the common methods of single-quantum NMR spectroscopy. The book presents also the data of two-dimensional correlation NMR spectroscopy as the distributions of diffusion coefficients in two orthogonal directions on the systems with anisotropic mobility. Simulations of two-dimensional NMR experiments have been done showing how it leads to the explanation of 2D experimental data on the anisotropy of diffusion coefficients. These 2D NMR methods reveal microscopic local anisotropy by the correlation of the diffusion motion of molecules along either collinear or orthogonal directions of applied pulse gradients of magnetic field.
It is shown that combination of NMR relaxation and diffusion (one- and two-dimensional) techniques is effective experimental methodology which is able to produce valuable information on the dynamic properties and anisotropy in natural silk and collagen fibers with various cross-links, synthetic polymers and porous heterogeneous systems, such as wood and cement.
Both collagen and thread produced by silk worm Bombyx mori are used in nano-scaffolds fabrication for tissue engineering applications. One of the most features of new-created scaffolds with stable chemical cross-linking is a control of the mechanical properties which change the tissue hydration and macromolecular content. Changes in tissue hydration, water-fiber interactions, and macromolecular content can be reflected by NMR. With detailing the hydration properties of collagens at different cross-linking level by NMR, a role of water interactions in improving scaffold characteristics for tissue engineering could be clarified. The book considers how NMR highlights the interaction of these natural fibrous materials with water. Natural silk Bombyx mori is also known as one of the strong natural biomaterials. Bombyx mori silk fibers have two protein-monofilaments embedded in the glue-like sericin coating. The interaction of these natural materials with water leads to a decrease in the length of silk fibers. One chapter of the book shows how natural silk Bombyx mori with low water content has been studied by 1H DQF NMR and single-pulse 1H NMR methods. That investigation demonstrated that DQF NMR enables one to probe the anisotropic motion of water in the silk fibers with residual water content.
Polymers are frequently used as barrier coatings in the technology of many materials to prevent the degradation of porous substrates, for example, such as wood. Mostly, a barrier coating should regulate the transport of water. However, there is the fact that water has a solubility even in hydrophobic polymers. So, the questions of water-polymer interaction are essential in many technological stages of material production and could be answered by NMR studies. The penetration of water into polymer films had always increasing attention in material research. Diffusion of water in different polymer films has been extensively investigated in many research groups. Different NMR methods, in particular, NMR relaxometry and NMR spectroscopy have been used to characterize water molecules in the films during the drying process. These approaches have developed the possibilities of identification of different environments for water upon drying the film or in the films swollen in water. The chapters of this book considered also how the diffusivity and distribution of water in polymer films have been investigated using the NMR relaxation and PFG NMR techniques. The contributions of polymer matrix protons, surface water and bound water could be determined from NMR relaxation functions and 1H NMR spectra. The PFG NMR experiments discovered that the echo-attenuation function depends on the diffusion time indicating that water inside the swollen film is trapped in restricted confinement. The published physical models for diffusion of water in polymeric materials have been probed to fit experimental results. As a result, NMR applications were successful in estimating the sizes of pores inside the polymer films. Thus, the studies described in the book established how magnetization decays and the spin-spin relaxation times of water in saturated polymer films could be applied to provide additional information on the water distribution in the porous microstructure.
Wood is one of the most important natural fiber composites. This material is applied in construction area. For fibrous material, the diffusivities of water could be different along the fiber and in the direction of perpendicular to fiber axis. The book considers how to use one- and two-dimensional PFG NMR spectroscopy to explore the anisotropic diffusion of water in wood. Findings herein suggest that it is possible to directly register diffusion anisotropy by one-dimensional PFG NMR as well as to visualize it in 2D maps of wood. These approaches can potentially be used to diagnose and monitor the treatment of wood that involves macromolecular reorganization and associated changes in cross-relaxation and molecular diffusion of water. The methods are applicable for investigating wetting/drying wood. It can be used also in studying modifications of wood technology affecting the diffusion anisotropy of water in wood cells.
Cement pastes are the examples of heterogeneous porous materials with slow water dynamics. Cement reacts with water to form an amorphous paste through the chemical reaction called hydration. It is plastic and soft when newly mixed, strong and durable when hardened in concrete. The character of the concrete is determined by the quality of the paste. To better understand the role of water in mature concrete, it is necessary to understand a diffusion transport of water in cement pastes cured for different ages: from few hrs to few months. The results of one- and two-dimensional PFG NMR diffusometry studies of water in white cement paste aged from 1 day to 1 year show that the NMR PFG method is primarily sensitive to the capillary porosity. Data is fit on the basis of a log-normal pore size distribution with pore size dependent relaxation times. The volume mean capillary pore size is 4.2 μm in mature paste. No evidence is found of capillary pore anisotropy in cement paste.
Hopefully, the NMR results considered would allow one to get more details in description of diffusion anisotropy and properties of different materials in future.
The book is based on the results of own studies and publications. However, all considered data are discussed and compared with literature data presented in this area and used in the context of total directions of the book to highlight main conclusions of NMR studies in polymers, natural biopolymers, and construction materials.
The text of the book is aimed for researchers. However, the level appropriates to a graduate student in physics, mathematics and/ chemistry. The biologist reader may omit mathematical aspects / equations at first reading and find many useful information on NMR applications in biomaterials. The book will be interest and help to both those need to learn additional NMR applications and those needing to refresh their knowledge and extend their own NMR capabilities. Though the book starts at a useful elementary level on basic NMR it goes deeply into the various NMR applications in studying natural biological and synthetic materials. On the other hand, the author mentions / discusses only very briefly certain special matters in NMR which are outside the scope of this book. Hopefully, the material considered is that many readers will find of interest.
Dr. Victor V. Rodin
Institute of Organic Chemistry
Johannes Kepler University Linz
4040 Linz, Austria
Conflict of Interest
The author declares no competing interest regarding the publication of this book.
List of Contributors
Victor V. Rodin