Langmuir, Vol.16, No.24, 9221-9224, 2000
Aggregation behavior of urocanic acid bolaamphiphiles
Symmetrical bolaamphiphiles derived from (E) urocanic acid (3-[1H-imidazolyl-(4)-yl]-propenoic acid) were prepared and their self-assembling properties examined. The morphologies of the aggregates formed by these amphiphiles in aqueous solutions have been found to be strongly dependent on three parameters (pH, structure, and position of the connecting links). For the N-alkylated derivatives, vesicles are obtained irrespective of the pH. For the O-alkylated derivative with an ester linkage, the hydration of the imidazolium headgroup led to the formation of spherical aggregates. With an amide linkage, amphiphiles can self-assemble to give interesting aggregates that can be tuned by changing the pH. In acidic media, two kinds of aggregates are observed: rigid rods and flexible water-filled tubules. These investigations reveal that the number and the position of the functions generating hydrogen bonding play a key role in the type of aggregate formed. Hydrogen bonding encourages the formation of fibers.