Preface

Summary

Liquid crystals (LCs) are unique functional soft materials which combine both order and mobility on a molecular, supramolecular and macroscopic level. Hierarchical self-assembly in LCs offers a powerful strategy for producing nanostructured mesophases. Molecular shape, microsegregation of incompatible parts, specific molecular interaction, self-assembly and self-organization are important factors that drive the formation of various LC phases. LCs are accepted as the fourth state of matter after solid, liquid and gas. LCs form a state of matter intermediate between the solid and the liquid state. For this reason, they are referred to as intermediate phases or mesophases. This is a true thermodynamic stable state of matter. The constituents of the mesophase are called mesogens. Since the discovery of LCs in 1888 by F. Reinitzer, it was assumed that LC molecules are mainly composed of mesogenic core attached to which are one or more alkyl chains. However, during 1980s a new class of LCs attracted particular attention acknowledged as the LC dimers. An LC dimer is composed of molecules containing two mesogenic units linked via a flexible alkyl spacer, most commonly an alkyl chain. Thus, LC dimers contravened the accepted structure–property relationships for low molar mass mesogens by consisting of molecules having a highly flexible core rather than a semirigid central unit. In these respect, therefore, these molecules actually represented an inversion of the conventional molecular design for low molar mass mesogens. Although this class of compounds has been discovered by Vorlander long back in 1927, these dimers did not achieve considerable attention until their rediscovery by Griffin and Britt in 1980s. Subsequently, several classes of dimeric LC compounds have been prepared and studied extensively.

As of now, no book exists on this topic. However, a chapter on LC dimers can be seen in many LC-related books. While a number of books are available on LCs, no exclusive book describing the basic design principles, transitional properties, device fabrication and applications of dimeric LCs is available. Researchers working in the field of LC dimers and device fabrication need to have an upto- date source of reference material to establish a solid foundation of understanding. It is extremely important that students and researchers in this field have ready access to what is known and what has already been accomplished in the field. This book contains all the recent literature up to 2015 and covers the physics, chemistry, electronics, and materials-related properties.