Azobenzene-cholesterol

Kumaresan S, MaUia VA, Kida Y, Tamaoki N. 2005. Thermal and photooptical properties of azoxybenzene/alkyloxy azobenzene cholesterol dimesogens with alkyl diacetylene linker. J Mater Res 20(12) 3431 3438. 

Sakurai et al. have employed synchrotron SAXS to support a previously proposed model [54] for molecular arrangement in a helical fiber of an azobenzene-cholesterol-based gelator (6) [52a]. A hollow cylinder model exhibited better agreement with the experimental SAXS profile than a solid cylinder model. 

Chen, X., Xue, Q. B., Yang, K. Z., Zhang, J. Z., and Zhang, Q. Z. Monolayer Behaviours for the Photochromic Liquid Crystalline Copolymers with Azobenzene and Cholesterol Side Groups. Supramol. Sci. 5, 591 (1998). 

Block copolymers of butadiene and styrene are therefore readily synthesized an-ionically, with either of the two monomers polymerized first. Precursor copolymers of poly(styrene-h/oc -butadiene) have been used to prepare well-defined liquid crystalline block copolymers by the same polymer analogous reaction described in Sec. 2.5 of this chapter (Scheme 21) [201-203]. Following anionic polymerization by sequential monomer addition, the polymer analogous reactions of the cholesterol (PS-PBCh) [201] and azobenzene (PS-PBAz) [203] derivatives were essentially quantitative, while that of the phenyl benzoate (PS -PBBz) block went to up to 94% conversion [202]. The polydispersities of the liquid crystalline copolymers (pdi= 1.13-1.23) were nearly as narrow as those of their precursor copolymers (pdi = 1.08 -1.21, M =8.09-9.2xl0 ) [201, 203]. 

Tamaoki N, Aoki Y, Moriyama M, Kidowaki M. 2003. Photochemical phase transition and molecular realignment of glass forming liquid crystals containing cholesterol/ azobenzene dimesogenic compounds. Chem Mater 15(3) 719 726. 

An important class of azobenzene-based ALS organogelators is that of cholesterol derivatives bearing a crown ether moiety at the azobenzene unit, such as compounds 32-2, 33, and 34X (Scheme 12). Compound 32-2 with... 

Scheme 12 Azobenzene-appended cholesterol LMOGs bearing a crown ether moiety display metal-cation sensitive gelation ability...

Scheme 13 Azobenzene-appended cholesterol LMOGs bearing pendant ammonium or diamine units as effective gelators of polar organic solvents...

Particular emphasis should be placed on the preparation and smdies of oligomeric cholesteric cyclic siloxanes containing cholesterol (Choi) and various mesogeitic fragments (R), such as binaphol phenyl benzoate, azobenzene derivatives. ... 

Azobenzene-based gelators have been studied extensively, because spectroscopic properties of the azobenzene moiety afford useful information on how the molecules are assembled and how the gel is formed. A typical sample was azobenzene-appended cholesterol gelators 22a-e, in which azobenzene 7T-7T Stacking and cholesterol-cholesterol interaction cooperatively stabilize the organogel structure as described in Sect. 2.1.1 (Fig. 15) [12,13]. Hydro-... 

---