Self-aggregation, Temperature-responsive Agglutination, and pH-induced Disaggregation of Amphiphilic Cyclophane Dimer Having a PEG Linkage

An amphiphilic cyclophane dimer (1), which was constructed with two cyclophane skeletons, each having three hydrophobic side-chains with Boc-protecting amino groups, and a hydrophilic polyethylene glycol (PEG) linkage, was synthesized. Amphiphilic compound 1 was found to form self-aggregate in aqueous media. In addition, 1 exhibited lowest critical solution temperature (LCST) behavior and its aqueous solution became turbid above the LCST upon heating. Moreover, pH-induced disaggregation of the self-aggregates of 1 was successfully performed upon addition of hydrochloric acid, to produce a cationic water-soluble cyclophane dimer (2) by the removal of the Boc-protecting groups of 1. Amphiphilic cyclophane dimer 1 was found to form self-aggregate. pH-Induced disaggregation of the self-aggregates of 1 was successfully performed upon addition of hydrochloric acid, to produce cationic water-soluble cyclophane dimer 2 by the removal of the Boc-protecting groups. In addition, 1 exhibited LCST behavior and its aqueous solution became turbid above their respective LCST upon heating.