Vol.5 No.3 2012

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Research paper : Novel functional gels and their commercial distribution as chemical reagents (M. Yoshida)−184−Synthesiology - English edition Vol.5 No.3 (2012) presence of an appropriate base under refluxed condition. To realize a new material that could be mass-produced, as mentioned before, one of the synthesiological elements was “to use the commercially (easily) available starting materials.” Precisely said, this reaction occurs in two steps of primary amidation and the following intermolecular quaternization reaction. However since the reactivity of the intermediate produced in the first reaction is high and the second step reaction ensues quickly, it looks like a single step “one pot reaction.” It is known that the material is the “oligomer” (polymer with relatively low molecular weight) with average degree of polymerization (n) of 10 to 20.[4][5] There is very few case of synthesis of organic electrolytes by self-condensation, and this is a novel synthetic approach that is totally different from the conventional polymerization where two types of monomers must be prepared beforehand. This is characterized by “a small number of steps” needed to solve the problem, and can be considered an important element of synthesiology.4.2 Gelation behaviorA hydrogel can be easily made from the organic electrolyte oligomer obtained, using a method similar to that for the conventional physical gelators. The powder is added to the water at a concentration of 1 weight % or more, the process of heating dissolution at high temperature cooling (by leaving at room temperature) is done, and the water can be gelated (Fig. 4 left).As a general characteristic of the physical gel, this gel undergoes thermal and reversible gel-sol transition, and the once quasi-solidified gel becomes a solution without high viscosity by heating. Although the clear mechanism of gelation is not yet clarified, it is likely that the electrostatic interaction plays an important role, and other diverse interactions are involved in a complex and complementary manner. As mentioned later, this gelator possesses affinity to carbon nanotubes (CNTs). Therefore, complexation with CNTs can be done easily, and we were able to prepare a CNT-containing gel by only the electrolyte gelator (Fig. 4 right).4.3 Numerous functions of electrolyte gelatorThe oligomeric electrolyte has interesting characteristics that were difficult or could not be achieved at all by existing gelators, as shown below.4.3.1 Acid resistanceIn naturally derived gels, the gel cannot be made using an acid solution because the main molecular structure disintegrates under acid conditions. However, it was projected that the new material would be acid resistant because it does not possess the acid labile functional groups. By using this material, the gelation of an acid water solution with about pH=1 was achieved, and application may be possible for the quasi-solidification of acid waste liquids that used to be a challenge (on the other hand, since the solubility of the gelator decreases in the base condition, gelation has not been successful).4.3.2 Solvent compatibility control by anion exchangeThe electrolyte gelator is composed of the organic part with cation and the corresponding anion, and the initial anion after the preparation is the chloride that is the same as common salt (sodium chloride). By replacing the anion with a different anion, it is possible to control the solubility (compatibility) of the gelator. This can be applied to solvents other than water, by controlling the gelator compatibility as the chloride ion of the parent compound is replaced with hydrophobic fluorinated anions such as N(SO2CF3)2 and PF6 that are typical counter ions in ionic liquids known as the new functional solvents.[4][5] This can be used for the gelation of various organic solvents and the aforementioned ionic liquids, not just water (Fig. 5). Therefore, the characteristic distinct from the conventional artificial gelators is that the solubility can be easily adjusted even after synthesis by the counter anion exchange, and in the sense that it possesses a single molecular skeleton, it is the realization of an “amphiphilic Fig. 3 Synthesis of the electrolyte gelator==CH2CI2CH2CICH2CIEt3NCIOONH2NNNH+nH2CCIONNHH2CCIONNHCH2CIONNHn

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