Thermosensitivity of Bile Acid-Based Oligo(ethylene glycol) Stars in Aqueous Solutions

Arnphiphilic star-shaped oligo(ethylene glycol)s with a hydrophobic bile acid core and varying number of hydrophilic arms have been made. Their thermal behavior in aqueous solutions depends on the number rather than the length of the arms. The two-armed lithocholate derivative showed the strongest tendency for association and exhibited the lowest cloud point (79 degrees C) of the oligomers made, as well as another phase separation at a lower temperature (31 degrees C). The double thermosensitivity arising both from the salt-dependent LCST of the oligo(ethylene glycol) segments and the temperature-responsive self-assembly of amphiphilic bile acid derivative provides an interesting path in the design of bile acid-based smart materials.