Mariko Yumoto

In situ organogelation at room temperature: direct synthesis of gelators in organic solvents

Organogels are formed through a conventional organogelation involving a heating process and an in situ organogelation at room temperature. The conventional organogelation is carried out by dissolution of gelators by heating, while the in situ organogelation is performed by mixing of highly reactive methyl 2,6-diisocyanatohexanoate (LDI) or 2-isocyanatoethyl 2,6-diisocyanatohexanoate (LTI) and alkylamines. The in situ organogelation produced the organogels within several seconds after mixing. The organogels prepared by the in situ organogelation showed quite similar FT-IR spectra and SEM photographs to those formed by conventional organogelation. Moreover, the in situ organogelation using LTI and octylamine as well as dodecylamine produced organogels of acetone, ethyl acetate, and acetonitrile that gelators 5 and 6 cannot gel through conventional organogelation.

Novel dumbbell-form low-molecular-weight gelators based on L-lysine: their hydrogelation and organogelation properties

New L-lysine-based, dumbbell-form, low-molecular-weight gelators, in which two L-lysine derivatives are linked by alkylene spacers, were synthesized and their gelation abilities for aqueous solutions and organic solvents were examined. These gelators are amphiphilic gelators that function as not only hydrogelators but also as organogelators. In hydrogels, these gelators created a three-dimensional network by entanglement of self-assembled nanofibers via hydrogen bonding and van der Waals interactions. The hydrogel-broken temperatures (Tgel) depended on the carbon numbers of the alkylene spacers and showed an odd–even effect. The FT-IR and 1H-NMR spectra demonstrated a difference in the intermolecular hydrogen bonding modes between the gelators of the even-numbered chains and odd-numbered chains.

Novel family of low molecular weight hydrogelators based on L-lysine derivatives.

New L-lysine derivatives with a positively charged terminal can gel water below 1 wt%; particularly, 1a and 2a form a hydrogel at 0.3 wt% corresponding to approximately 12,300 and 12,500 waters/gelator molecule, respectively.

New gemini organogelators linked by oxalyl amide: organogel formation and their thermal stabilities

New gemini organogelators linked by an oxalyl amide that can be easily, effectively, and cheaply synthesized have good organogelation abilities and their cyclohexane gels have superior thermal stabilities; especially 7 possessing the branched alkyl ester can gel at 0.7 wt% cyclohexane even at 70°C.

L-Lysine-based supramolecular hydrogels containing various inorganic ions

The preparation of supramolecular hydrogels containing various inorganic acids and salts using L-lysine-based hydrogelators is conducted and their thermal stabilities, gel strengths, FT-IR spectra, and electron micrographs are measured. These hydrogelators can form supramolecular hydrogels over a wide pH range and contain inorganic acids and salts. The supramolecular hydrogels based on ester-type hydrogelators have good thermal stabilities (high Tgel), while the hydrogelator with a carboxyl group forms a thermally sensitive gel with high mechanical strength. Furthermore, the gelation mechanism is discussed using FT-IR spectroscopy and TEM observations.

New low-molecular-weight hydrogelators based on L-lysine with positively charged pendant chain

New low-molecular-weight gelators, L-lysine derivatives with a positively charged terminal in the ester group, can gel water at low concentrations; in particular, 1 and 8 form a hydrogel at 0.1 wt%.