| Gemini supramolecular amphiphiles are assemblies of gemini surfactants which are joined by non-covalent bonds including hydrogen bonds,host-guest interactions,charge transfers,?-? stacking interactions,metal-ligand coordinations as well as electrostatic interactions.Dynamic covalent bonds also play an irreplaceable role in building gemini supramolecular amphiphiles.In contrast to traditional gemini amphiphiles which are fabricated by covalent bonds,it is accessible in both laboratory and industrial scales to prepare gemini supramolecular amphiphiles without tedious and time-consuming processes,in addition use of water as a solvent is not hazardous to the environment.Meanwhile,gemini supramolecular amphiphiles have capacity of forming sophisticated and well-ordered structures as well as,multiple morphologies in self-assembly process exhibiting superior characteristics and versatile functionalities compared with their single tailed counterparts under external stimuli such as light,temperature,pH,CO2 and so on.In first experiment,we initially studied the dynamic covalent bonds played an important role in construction of gemini superamolecular surfactants.Dynamic gemini surfactants,which was based on Schiff base principle that hydrazone bounds can dynamically form in water under acid conditions owing to its possess higher stability,were prepared,so amphiphile with single-tailed structure can turn into two-tailed one,and the detergent's efficiency and effectiveness of lowering the surface tension of water will be augmented at optimum working environments.Owing to poor solubility of gemini supramolecular surfactants and long distance between the two hydrophobic tails which spacer did not play the crucial in reducing the repulsion between hydrophilic head groups,the ideal result at reducing surface tension was not obtained,however we believe that such dynamic detergent systems can open the door to industrial research that employs surface active agents as examples that enhance their properties in a non-linear fashion.In the second experiment,we imported the concepts of template-modulated micellization into donor-acceptor charge transfer interactions to investigate how rigid spacers with different length to gemini amphiphiles based on ?-electron deficient bis-bipyridinium functional unit(13-15·4Cl)and melatonin.Three gemini surfactants with different length of spacers adopt and hold a "horseshoe-shaped" conformation in aqueous solution and melatonin can perfectly be embedded in cavity detected by DOSY,which resulted in dramatic raise in their efficiency and effectiveness at lowering the surface tension of water.With spacer length increasing from 2.3 A to 7.1 A,13·4Cl(?)melatonin exhibited the best solubility,therefore this superamolecular complex showed excellent surface activity on comparison of 14-15·4Cl(?)melatonin and this result was further proved by dynamic light scattering(DLS),electrochemistry,UV-Vis titration experiments and transition temperatures of thermochromic pictures.Variable temperatures conductivity experiments showed all the micellization processes were spontaneous and entropy-driven,besides the values of standard enthalpy(?HM°)were all negative,which proved that micellization was exothermic process.For the three superamolecular soft matters,with temperatures gradually increasing,the ?SM°gradually decreased to zero and ?HM° gradually become dominant to changing of ?GM°,so there was existence of enthalpy-entropy complementary phenomenon.Besides the superamolecular complexes of 13-15·4Cl(?)melatonin possessed thermochromic property which mean it can be used in the preparation thermochromic inks to print pattern that broadens its application. |
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