Carbosilane liquid crystalline dendrimer containing twelve 4-hexyloxyazobenzene mesogenic groups

The divergent synthesis of a new carbosilane liquid-crystalline(LC) dendrimer(D1) was described. Twelve 4-hexyloxyazobenzene groups (M3) were used as mesogenic fragments and-attached to its periphery. Structure and properties of D1 were characterized by means of elemental analysis, H-1 NMR, IR, UV, MALDI-TOF-MS, polarizing optical micrograph, DSC and WAXD. D1 is a nematic liquid crystal, which is the same as M3. The mesomorphic behaviour of the dendrimer depends on that of the mesogenic units. Phase behavior of D1 is K92N126I124N78K. m. p. of Ell is 24-30 degreesC lower than that of M3, its clearing temperature is 13-8 degreesC higher than that of M3 and its mesophase region is 30 similar to 38 degreesC wider than that of M3. The clearing enthalpy of D1 accords with the value that is commonly found for n-i phase transition in LC and LC polymers. This may be due to the deformation of branched dendrimer D1 which can be change to fit into the anisotropic LC phase structure. Eight extinguished brushes emanating from a stationary point are observed, corresponding to the high-strength disclination of S = + 2 of dendrimer.