| dc.description.abstract | In the first series, for new series of unsymmetric isoxazoles、pyrazoles and 1,3,4-oxadiazoles were prepared, characterized and their mesomorphic properties investigated. Isoxazoles were obtained by condensationcyclization of –diketones with hydroxylamine hydrochloride in refluxing THF,and pyrazoles obtained by condensationcyclization of –diketones with hydrazine in refluxing THF，while 1,3,4-oxadiazoles were obtained from hydrazine–carboxylate in refluxing POCl3.The data indicated that all compounds with meta-substituted benzene1b、3bwere not mesogenic. Interestingly, the other series of compounds with para-substituted benzene1a、2a、3aexhibited N/ SmC /SmA phases. The formation of mesophases in 1a、2a、3a might be attributed to the better linear molecular shapes. In contrast, all compounds 1b、3b were more likely bent-shaped,for mesomorphic.
In the second series, a system of isoxazole containing function group of hydroxyl, performed reaction of condensation reaction then exhibition mesomorphic properties was synthesize and examined. 4a exhibited SmX/SmC phase. Results indicated that increasing the pryazoles would raise the isotropic temperatures and increasing the OH function group would supply hydrogen bonds for molecular arrangement regularity. These mesomorphic properties were studied and identified by polarization microscopy, differential scanning calorimetry, and X-ray diffraction methods. | en_US |