Aggregation and photoresponsive behavior of azobenzene-oligomethylene-glucopyranoside bolaamphiphiles

The self-aggregation behavior of a series of photoresponsive bolaamphiphiles consisting of a central azobenzene moiety linked to terminal sugar groups via oligomethylene spacers in water/DMSO mixed solvents are reported. Changes in the absorption spectra in these solvent mixtures indicated the formation of tightly packed H-aggregates. The ease of formation and the stability of the aggregates were observed to increase with increase in the length of the oligomethylene spacers. Microscopic studies indicated the formation of vesicles or fibers depending upon the length of the oligomethylene spacers. Disruption of the aggregates induced by photoisomerization of the azobenzene unit and their reformation via the subsequent thermal cis to trans isomerization was also investigated