Design, synthesis, and characterization of cross-linkable, polycatenar liquid crystals with light-emitting capabilities

Conjugated organic materials possess a number of interesting optical and electronic properties that have recently found practical applications in light-emitting diodes (LEDs) and field-effect transistors (FETs). The organization of these materials has a profound effect on their efficiency. Liquid crystals (LCs) offer excellent control over important parameters such as orientation, organization, and symmetry on the molecular level. This control is a means of constructing new functional materials with tailored anisotropic properties, and the incorporation of emission properties into organic LCs is the focus of this work.; Chapter One provides an overview of LCs and light-emitting organic materials. The goal of this project is to develop fluorescent LC monomers with cross-linking capabilities that is outlined at the end of Chapter One. Polymerization of the monomer in its mesophase affords a rigid, three-dimensional network with retention of anisotropy and nanometer-scale order. These networks display high thermal stability and may have applications as organic LEDs.; Chapter Two presents the design, synthesis, and characterization of nonpolymerizable, luminescent LCs. Mesogens were developed from a phasmidic LC architecture and incorporated an oligo(p-phenylenevinylene) core as the fluorescent moiety. These systems form columnar, hexagonal (Φ_h) phases, and structure–property relationships of the LC were studied. The effects of nanometer-scale anisotropy on photophysical properties were also investigated.; Chapter Three considers cross-linkable analogues of the luminescent, phasmidic LCs developed in Chapter Two. Traditional polymerizable groups suppress LC behavior in these systems, so a novel linear 1,3-diene tail system was developed. The influences of this new polymerizable group on mesogenic behavior are discussed in Appendix One. Phasmidic monomers incorporating 1,3-dienes display the Φ_h phase and were successfully cross-linked by thermally-initiated polymerization. The resulting anisotropic networks retain the nanometer-scale order imparted by the LC phase and remain highly luminescent.; Chapter Four details the synthesis and phase behavior of luminescent tetracatenar LCs. The nonpolymerizable mesogens exhibit rich mesomorphism dictated by tail length and show promise as possible polarized emitters. Cross-linkable analogues were developed but suffered from premature polymerization at the high transition temperatures of the mesophase.