Author: Gary DrobnyPublisher:
ISBN:
Category :
Languages : en
Pages : 648
Book Description
NMR Studies of Liquid Crystals and Molecules Dissolved in Liquid Crystal Solvents
Author: Gary DrobnyNMR Studies of Liquid Crystals and Molecules Dissolved in Liquid Crystal Solvents
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 324
Book Description
This thesis describes several studies in which nuclear magnetic resonance (nmr) spectroscopy has been used to probe the structure, orientation and dynamics of liquid crystal mesogens and molecules dissolved in liquid crystalline phases. In addition, a modern high field nmr spectrometer is described which has been used to perform such nmr studies. Chapter 1 introduces the quantum mechanical formalisms used throughout this thesis and briefly reviews the fundamentals of nuclear spin physics and pulsed nmr spectroscopy. First the density operator is described and a specific form for the canonical ensemble is derived. Then Clebsch-Gordon coefficients, Wigner rotation matrices, and irreducible tensor operators are reviewed. An expression for the equilibrium (Curie) magnetization is obtained and the linear response of a spin system to a strong pulsed r.f. irradiation is described. Finally, the spin interaction Hamiltonians relevant to this work are reviewed together with their truncated forms. Chapter 2 is a deuterium magnetic resonance study of two 'nom' liquid crystals which possess several low temperature mesomorphic phases. Specifically, deuterium quadrupolar echo spectroscopy is used to determine the orientation of the liquid crystal molecules in smectic phases, the changes in molecular orientation and motion that occur at smectic-smectic phase transitions, and the order of the phase transitions. For both compounds, the phase sequence is determined to be isotropic, nematic, smectic A, smectic C, smectic B{sub A}, smectic B{sub C}, and crystalline. The structure of the smectic A phase is found to be consistent with the well-known model of a two dimensional liquid in which molecules are rapidly rotating about their long axes and oriented at right angles to the plane of the layers. Molecules in the smectic C phase are found to have their long axes tilted with respect to the layer normal, and the tilt angle is temperature dependent, increasing from zero at the smectic A - smectic C transition and reaching a maximum at 9{sup o} at the smectic C - smectic B{sub A} transition. This finding contradicts the results of X-ray diffraction studies which indicate that the tilt angle is 18{sup o} and temperature independent. The smectic B{sub A} - smectic B{sub C} phase transition is observed for the first time, and is found to be first order, a result that contradicts the prediction of a mean theory by McMillian. Chapter 3 is a multiple quantum nmr study of n-hexane oriented in a nematic liquid crystal solvent. The basic three pulse multiple quantum experiment is discussed which enables the observation of transitions for which.
NMR Spectroscopy Using Liquid Crystal Solvents
Author: JW EmsleyPublisher: Elsevier
ISBN: 1483279944
Category : Science
Languages : en
Pages : 385
Book Description
NMR Spectroscopy using Liquid Crystal Solvents covers the importance of using a liquid crystal solvent in NMR to derive nuclear dipolar spin-spin coupling constants. This book is composed of ten chapters, and begins with a brief description of the features and benefits of liquid crystal in NMR spectroscopic analysis. The succeeding chapters deal with the mode of operation of nuclear spin Hamiltonian for partially oriented molecules and the analysis of NMR spectra of partially oriented molecules, as well as the determination of rigid molecule structure. These topics are followed by discussions on internal motion studies, NMR spectra from quadpolar nuclei, and the anisotropy in nuclear spin-spin coupling. The final chapters review the theoretical and experimental studies on the anisotropy in chemical shifts, nematic rotation, and the nuclear magnetic double resonance. This book will prove useful to analytical chemists.
Nuclear Magnetic Resonance of Liquid Crystals
Author: Ronald Y. DongPublisher: Springer Science & Business Media
ISBN: 146121954X
Category : Science
Languages : en
Pages : 320
Book Description
Intended for researchers and students in physics, chemistry and materials science, this book provides the necessary background information and sufficient mathematical and physical detail to study the current research literature. The book begins with a survey of liquid crystal phases and field effects, together with an introduction to the basic physics of nuclear magnetic resonance. It then discusses orientational ordering and molecular field theories for various liquid crystal molecules and nmr studies of uniaxial and biaxial phases. Subsequent chapters consider spin relaxation processes and rotational, translational, and internal molecular dynamics of liquid crystals. The final chapter discusses two-dimensional and multiple- quantum nmr spectroscopies and their application in elucidating liquid crystal properties. This second edition, updated throughout, incorporates many new references and includes new mathematical appendices.
NMR of Liquid Crystal Dendrimers
Author: Carlos Rodrigues da CruzPublisher: CRC Press
ISBN: 1315340747
Category : Science
Languages : en
Pages : 295
Book Description
Dendrimers are hyperbranched molecules with well-defined nanometer-scale dimensions. Important technological applications of these systems, both in biomedicine and materials science, have been recently proposed. Liquid crystal dendrimers are fascinating materials that combine the characteristics of dendrimers with the anisotropic physical behaviour and molecular self-organization typical of liquid crystals. This unique association of physical and chemical properties, together with the possibility of multi-selective functionalization put forward by dendrimers, opens new perspectives for applications. Nuclear magnetic resonance (NMR) is a powerful experimental technique applied in materials science and an important tool to the study of molecular organization and dynamics. This book presents an introduction to dendrimers properties with special insight into liquid crystal dendrimers and a detailed description of the NMR theory and experimental techniques used in the investigation of these materials. It also discusses recent NMR research results on liquid crystal dendrimers, with emphasis on molecular order and dynamics studies. This book introduces the properties of dendrimers, with special insight into liquid crystal dendrimers, and a detailed description of NMR theory and experimental techniques used in the investigation of these materials. It also discusses results of recent NMR research on liquid crystal dendrimers, with an emphasis on molecular order and dynamics studies. Advanced undergraduate and graduate students of physics, chemistry, and materials science and researchers in the fields of dendrimers, liquid crystals, and NMR will find the book extremely useful.
NMR of Ordered Liquids
Author: E.E. BurnellPublisher: Springer Science & Business Media
ISBN: 9401702217
Category : Science
Languages : en
Pages : 465
Book Description
NMR of Ordered Liquids gives a unique overview of the scope and limitations of the NMR of oriented liquids, based on contributions from acknowledged experts in the field. The book consists of four sections: -detailed general introduction which covers the basic principles and sophisticated experimental techniques; -wide variety of applications ranging from NMR studies of small atoms and molecules in anisotropic liquids to the utilization of residual dipolar couplings for structure determination of biological molecules; -summary of the sophisticated theoretical treatments, computer simulations, and phenomenological models for anisotropic intermolecular interactions that are widely used in the analysis of experimental results; -overview of the dynamical aspects and relaxation processes relevant for orientationally ordered molecules.
NMR Studies of Molecules in Liquid Crystals and Graphite
Author: Mark Edward RosenDynamic NMR of Molecules Dissolved in Liquid Crystalline Solvents
Author: Rachel NaorNuclear Magnetic Resonance of Liquid Crystals
Author: J.W. EmsleyPublisher: Springer
ISBN:
Category : Science
Languages : en
Pages : 602
Book Description
The liquid crystalline state has been known for about a century and has been studied by many techniques. Nuclear magnetic resonance has been used to study mesophases for thirty years, but it has been in very recent years that advances in this form of spectroscopy have led to a rapid growth in its applications to the study both of liquid crystals and of solutes dissolved in them. It has become apparent that no other method of studying liquid crystals can yield such a wealth of data and it is unrivalled as a means of probing the behaviour of the molecules in mesophases. There has also been a steady increase in the study of the shape of small molecules dissolved in liquid crystals via the analysis of their NMR spectrum. In fact, the study of solutes was until recently regarded as a separate activity to the study of liquid crystals themselves, but this artificial division arose only from the gap between the large amount of information that could be derived from the spectrum of a small molecule and the rather meagre data set obtainable from the spectra of liquid crystals. This gap has, however, narrowed and it is now possible to derive a very detailed picture of the structure and orientational ordering of the large molecules typical of those which form liquid crystals. There has also been a rapid growth of interest in the liquid crystalline state.
The Molecular Dynamics of Liquid Crystals
Author: G.R. LuckhurstPublisher: Springer Science & Business Media
ISBN: 9401111685
Category : Science
Languages : en
Pages : 612
Book Description
Liquid-crystalline phases are now known to be formed by an ever growing range of quite diverse materials, these include those of low molecular weight as well as the novel liquid-crystalline polymers, such phases can also be induced by the addition of a solvent to amphiphilic systems leading to lyotropic liquid crystals. Irrespective of the structure of the constituent molecules these numerous liquid-cl)'Stailine phases are characterised by their long range orientational order. In addition certain phases exhibit elements of long range positional order. Our understanding, both experimental and theoretical, at the molecular level of the static behaviour of these fascinating and important materials is now well advanced. In contrast the influence of the long range order; both orientational and positional, on the molecular dynamics in liquid Cl)'Stais is less well understood. In an attempt to address this situation a NATO Advanced Study Institute devoted to liquid ctystal dynamics was held at n Ciocco, Barga, Italy in September 1989. This brought together experimentalists and theoreticians concerned with the various dynamical processes occurring in all liquid crystals. The skills of the participants was impressively wide ranging; they spanned the experimental techniques used in the study of molecular dynamics, the nature of the systems investigated and the theoretical models employed to understand the results. While much was learnt it was also recognised that much more needed to be done in order to advance our understanding of molecular dynamics in liquid Cl)'Stais.