| Abstract
| - The structural factors influencing the self-assembly of aromatic side chain functionalized long chain acidsalts into lyotropic liquid crystal (LLC) phases were examined. Two sets of amphiphiles were synthesizedcontaining two different ionic headgroups (i.e., sodium carboxylate and sodium sulfonate) and four differentaromatic side chains (i.e., 4-styryl ether, 4-ethylphenyl ether, 1-naphthyl ether, and 4-phenylazophenylether) positioned at various locations along the amphiphile backbone. Systematic variation of the type ofthe aromatic side chain and its relative position on the amphiphile as a function of the two headgroupsrevealed that the position of the side chain on the amphiphile is the most important structural factorinfluencing the type and stability of the LLC phases formed. The nature of the aromatic side chain andthe nature of the anionic headgroup play much more subtle roles in the LLC behavior of this particularamphiphile structural motif. Noncovalent aromatic−aromatic interactions are known to play importantroles in the aggregation behavior of amphiphiles containing aromatic units along the alkyl chains; however,such interactions could not be detected spectroscopically in the LLC phases of our aromatic side chainamphiphiles. We speculate that the differences in alkyl chain interdigitation and packing efficiency arisingfrom having the aromatic unit as a side chain rather than along the alkyl chains are responsible for thisdiscrepancy. Control experiments with aliphatic ether side chain amphiphiles also corroborate the factthat aromatic interactions do not play a significant role in the aggregation behavior of these side chainamphiphiles. Side chain amphiphiles lacking an aromatic unit are still able to form the inverted hexagonalLLC phase, so long as the extent of branching and volume of the aliphatic side chain are sufficient.
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