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MRC special issue on NMR of liquid crystals

Nuclear magnetic resonance (NMR) is one of many experimental techniques that have been used for more than six decades to study the physical and chemical properties of liquid crystals (LCs). Liquid crystals consist of anisotropic soft matter that is intermediate between an isotropic liquid and a crystalline solid. These ubiquitous materials can be found in biology such as in membranes, in commercial products like soups and detergents, in display devices found in cell phones, television panels, and laptops and in industrial applications ranging from sensors and bio-robotic devices to molecular semiconductors. NMR has contributed very valuable information that is useful in all these fields. One of the characteristics of organic molecules forming LCs is their shape anisotropy, e.g.rod-like or disk-like. The shape anisotropy manifests itself in many ways, such as in dielectric and magnetic susceptibility anisotropy as well as in optical anisotropy. Technical applications of LCs in industry are one of the main driving forces for fundamental research of these materials. Since macroscopic physical properties of LCs and their anisotropies are closely governed by the orientational behavior of the molecules in the ordered mesophases, it is crucial to quantitatively determine liquid-crystal order parameters, for which NMR has played an important role. Of fundamental importance, the intrinsic anisotropic intermolecular potential between liquid-crystal molecules and/or between solvent LC and solute molecules can be gleaned from NMR spectroscopy. The behavior of LCs under external stimuli such as external electric/magnetic fields and/or anchoring interactions with surfaces is also crucial for proper LC applications. Besides directly studying these liquid-crystal materials, NMR of solutes dissolved in them is an invaluable tool for obtaining detailed information about various anisotropic nuclear spin interactions that are averaged to zero in the isotropic liquid, but remain in mesophases. Given the number of NMR active nuclei, the wealth of modern NMR pulse techniques and recent technical advances in NMR instrumentation, solid-state NMR has proven to be a valuable avenue for the investigation of orientational/positional order, molecular dynamics, chiral discrimination, mesomorphic phase structures and phase transitions in liquid crystals. This special volume aims to cover these topics. In fact it is a collection of articles that are written by experts to summarize recent advances in the field of NMR and in particular its applications to the liquid-crystal field. It is worth noting that since 2005, a group of NMR scientists has gathered every second year in a monastery in Tropea, Italy for a scientific conference entitled “NMR in Oriented Phases” to discuss how NMR can elucidate the physics and chemistry of liquid crystals. Many fruitful discussions during the free afternoons and collaborations among international participants have resulted from these meetings, including the idea of this special issue for Magnetic Resonance in Chemistry during an informal discussion over lunch at the last Tropea meeting. Most authors who have contributed original research, a review, a mini-review or a tutorial for this special issue are indeed past participants of the Tropea meeting(s). The diversity of subject matter (concerning solutes and/or LC solvents) should provide a tremendous source of information for readers, both un-initiated and seasoned, to the field of liquid crystals.