Preparation And Properties Of Novel Styrenic Liquid Crystal Polymers With Cholesteric Side Chains

As the "fourth state of matter", crystal polymers demonstrate promisingapplications in the fields concerning optoelectronics, materials, information,life and so on. Side chain liquid crystal polymers have been widelyinvestigated. For this type of interesting polymers, the structure of polymermain chains and side chains exerts large effects on the properties of thepolymer. Cholesteric groups contain chiral moieties and have been intensivelyutilized to prepare side chain liquid crystal polymers. Apart from this utility,the special chiral structures of cholesteric groups possibly enable the polymerbackbones to form helical structures and thus to display some uniqueproperties such as circular dichroism and optical activity. Due to the dualcharacteristics of both liquid crystal polymers and helical macromolecules,such liquid crystal polymers containing cholesteric side chains are consideredas a novel type of liquid crystal polymers with great potentials. Among theside-chain liquid crystal polymers, those with styrenic main chains areimportant because they are easy to prepare and design. However, only fewsuch liquid crystal polymers have been investigated in literature. This thesis is devoted to preparing novel styrenic liquid crystal polymers with cholestericside chains. The as-obtained polymers were characterized further in terms ofstructure and properties. The novel liquid crystal polymers lay somefoundation for the further development and application of liquid crystalpolymers with chiral side chains. The major contents in this thesis are stated asfollows:A novel styrenic liquid crystal monomer with a cholesteric side chain isprepared, and its properties are investigated in detail. The monomer itself wasproved to be a two-way thermotropic liquid crystal. The monomer underwentfree radical polymerizations, providing novel styrenic liquid crystal polymerswith cholesteric side chains. The main chains of such polymers are differentfrom those of the usual liquid crystal polymers with cholesteric side chains.This kind of liquid crystal polymers has a relatively larger liquid crystaltemperature range, and the temperature of the clearing points is relativelyhigher. We made a comparison between the properties of the liquid crystalmonomers and the polymers thereof; and further studied the influence ofmolecular weight of liquid crystal polymers on their properties. CD spectrademonstrated that the polymers adopted helical structures. Thethermodynamic analyses confirmed the polymer’s bidirectional thermotropicliquid crystal characteristics.By using ATRP polymerization, we prepared styrenic liquid crystalpolymers with cholesteric side chains aiming at exploring the influence of molecular weight on the crystal properties of the polymers. The polymers weresubjected to structural characterizations. Their liquid crystal properties werefurther investigated. We also performed NIPAm polymerization by the use ofthis polymer obtained above as macromolecular initiator, with a hope toprepare amphiphilic liquid crystal polymers and further to investigate theeffects of molecular structure on the polymers.