Bolaamphiphile: von Golfbällen und Fasern

Macroscalar Helices Co-Assembled from Chirality-Transferring Temperature-Responsive Carbohydrate-Based Bolaamphiphiles and 1,4-Benzenediboronic Acid

We present the first example of macroscalar helices co‐assembled from temperature‐responsive carbohydrate‐based bolaamphiphiles (CHO‐Bolas) and 1,4‐benzenediboronic acid (BDBA). The CHO‐Bolas contained hydrophilic glucose or mannose moieties and a hydrophobic coumarin dimer. They showed temperature‐responsive reversible micelle‐to‐vesicle transition (MVT) in aqueous solutions. After the binding of carbohydrate moieties with boronic acids of BDBA in their alkaline solutions, right‐handed helices were formed via the temperature‐driven chirality transfer of d‐glucose or d‐mannose from the molecular to supramolecular level. These helices were co‐assembled by unreacted BDBA, boronate esters (B−O−C bonds) between CHO‐Bolas and BDBA, as well as boroxine anhydrides (B−O−B bonds) of self‐condensed BDBA. After heating at 300 °C under nitrogen, the helices displayed excellent morphological stability. Moreover, they emitted bright blue luminescence caused by strong self‐condensation of BDBA and decomposition of coumarin dimers.

Langmuir monolayer properties of perfluorinated double long-chain salts with divalent counterions of separate electric charge at the air-water interface

The novel perfluorinated double long-chain salts with divalent counterions of separate electric charge, 1,1-(1,omega-alkanediyl)-bispyridinium perfluorotetradecane- carboxylate [CnBP(FC14)2 : n = 2, 6, 10, 14], were newly synthesized and their interfacial behavior was investigated by Langmuir monolayer methods. Surface properties [surface pressure (pi)-, surface potential (DeltaV)-, dipole moment (micro perpendicular)-area (A) isotherms] and morphological images of CnBP(FC14)2 monolayers on a subphase of water and on various NaCl concentrations were measured by employing the Wilhelmy method, the ionizing electrode method, fluorescence microscopy (FM), and Brewster angle microscopy (BAM). CnBP(FC14)2 formed a stable monolayer on water at 298.2 K, where these pi-A isotherms shifted to a larger molecular area with increasing charge separation and had no transition point from a disordered phase to an ordered one. On the contrary, the pi-A isotherms on NaCl solutions moved to the smaller areas, showed the transition and higher collapse pressures compared to the pi-A isotherms on water. These results suggested that a sodium chloride subphase induced the condensation of CnBP(FC14)2 molecules upon compression. In addition, it is quite noticeable that a dissociation of CnBP counterion from CnBP(FC14)2 occurs on NaCl solutions, depending on the extent of charge separation. This phenomenon was supported by the changes of the limiting area, transition pressure, collapse pressure, repeated compression-expansion cycle curve, and DeltaV behavior of perfluorotetradecanoic acid (FC14). Furthermore, temperature dependence of these monolayers was investigated, and an apparent molar quantity change on the phase transition was evaluated on 0.15 M NaCl. The morphological behavior of CnBP(FC14)2 and FC14 monolayers was also confirmed by FM and BAM images.