Synthesis And Properties Of New Type Pyrimidine Liquid Crystals

As environmentally friendly materials,liquid crystals(LC) are showing greater and greater application future in the field of flat panel display. In order to need the demends of novel LC display,it is very important to synthesize new LC materials and study the structure-propetry relationship of the compounds.In this paper, five new type pyrimidine LC compounds were designed and synthesized. The purities of all these compounds were tested by GC or HPLC, and their structures were identified by IR, 1H-NMR ,13C-NMR and GC-MS. The mesomorphic properties of the compounds were observed and measured by DSC (differential scanning calorimetry), respectively. The influences of terminal groups, ring systems and lateral substituents on properties of liquid crystals were investigated as well. Furthermore, 4-bromo-2,3-difluorophenol was separated with a new method.The main results are as follows:By using 2-hydroxypyrimidine hydrochloride as starting compound,intermediate 5-bromo-2-chloro pyrimidine was prepared through two-step reactions which were bromization,chlorization. The target compounds 5-Trans-5-[4-(4-alkylcyclohexyl)pheny]l-2-chloro pyrimidine were synthesized by the final coupling reacation of 5-bromo-2-chloro pyrimidine with trans-4-(4-alkylcyclohexyl)phenylboric acid.4,4'-di(5-propylpyrimidine)biphenyl was synthesized by using the starting compound ,pentanal and 4-bromobenzonitrile,through four-step reactions .The four chloropyrimidine LC compounds have high melting point and clearing point. The clearing points of this series compounds show odd-oven effect with the increasing of carbon atom number in the alkyl group. These compounds also show high polarity and dielectric anisotropy(Δε)and optically anisotropy (Δn).