| In this thesis, the synthesis and liquid crystalline properties of a series of novel substituted dibenz[a,c]anthracenes is reported. Specifically, a series of hexaalkoxydibenz[a,c]anthracenes were prepared and found not to exhibit a mesophase. In contrast, when substituents are introduced on the aromatic core, columnar mesophases are observed over broad temperature ranges. A series substituted derivatives was prepared and their mesomorphic properties compared. In general, electron-withdrawing substituents promote broad mesophase temperature ranges, as do larger substituents. The liquid crystalline phase is a result of the electronic effects, size and shape of the substituents in the 10 and 13 positions.;We also synthesized a series of discotic compounds based on substituted dibenzo[a,c]tetracenedione, dibenzo[a,c]pentacenedione and tetrabenze[a,c,d,f]pentacenedione, with 4, 4 and 8 aliphatic side chains, respectively, using similar methodologies to that of the dibenz[a,c]anthracene compound. These compounds were also found to exhibit columnar mesophases. The mesophase temperature range suggests that the larger aromatic core stabilizes both the crystalline and liquid crystalline phases. The dione functional groups also give a synthetic handle for further synthetic modifications to probe the structure-property relationships of these PAHs. |
