Fumiyasu Ono

Structural optimization of super-gelators derived from naturally-occurring mannose and their morphological diversity

Mannose derivatives were synthesized as low molecular-weight gelators with various alkoxy substituents on the aromatic ring of methyl-4,6-O-benzilidene-α-D-mannopyranoside . Most of these mannose derivatives could gel in various solvents, such as octane, cyclohexane, toluene, ethylene glycol and ethanol solutions, at concentrations lower than 2.0 wt%. In particular, the critical gelation concentration (CGC) of methyl-4,6-O-(4-butoxybenzylidene)-α-D-mannopyranoside (2) for squalane was only 0.025 wt%, one of the lowest CGCs we have ever experienced. The observations of xerogels by FE-SEM, TEM and AFM revealed that the length of the alkoxy chains of the mannose derivatives influences the gel morphologies. Moreover, the toluene gels formed from the mannose derivatives 1–6 functionalized by a linear alkoxy group exhibited thixotropic properties. Interestingly, the gels of various solvents formed from methyl-4,6-O-(4-dodecyloxybenzylidene)-α-D-mannopyranoside (6) (with the longest alkoxy chain on the aromatic ring in this paper) exhibited thixotropic properties. Thus, we confirmed that alkoxy groups on the aromatic ring exert noticeable effects on the gelation properties of these mannose derivatives.

Preparation of Microcapsules Containing β-Carotene with Thermo Sensitive Curdlan by Utilizing Reverse Dispersion

We have tried to microencapsulate β-carotene with curdlan of a thermogelation type polysaccharide. Microcapsules were prepared by utilizing reverse dispersion, in which salada oil was the continuous phase (O’) and the curdlan water slurry (W) was the dispersed phase. β-carotene (O) as a core material was broken into fine oil droplets in the dispersed phase to form the (O/W) dispersion. The (O/W) dispersion was poured in the continuous phase (O’) and stirred to form the (O/W)/O’ dispersion at room temperature and then, temperature of the dispersion was raised to 80 °C to prepare curdlan-microcapusles containing β-carotene. In this microencapsulation process, the concentrations of curdlan and oil soluble surfactant and the impeller speed to form the (O/W)/O’ dispersion were mainly changed stepwise. We were able to prepare microcapsules by the microencapsulation method adopted here. The content of core material was increased with the curdlan concentration and decreased with the impeller speed and the oil soluble surfactant concentration. With the curdlan concentration, the drying rate of microcapsules was decreased and the retention ability for water was increased due to the stable preservation of β-carotene.

High internal phase water/oil and oil/water gel emulsions formed using a glucose-based low-molecular-weight gelator

A high internal phase emulsion (HIPE) comprising silicone oil and water was prepared under surfactant-free conditions using low loadings of a glucose-based low-molecular-weight gelator capable of gelating both dispersed and continuous phases. The addition of an appropriate amount of a surfactant induced the inversion of the dispersed and continuous HIPE phases.

Solvent effect on the reversibility of base catalyzed Henry reactions : Triton B catalyzed nitro aldol reactions in alcohol

The amine catalyzed nitro aldol reactions between nitromethane and aldehydes are found to be reversible in an alcohol solvent on the basis of the reaction monitoring by 1H NMR spectroscopy. The reaction in alcohols is particularly rapid to complete the equilibrium in a short period of time at room temperature, producing nitro aldol product in high yields. Triton B is especially effective as catalyst in the nitro aldol reactions of nitromethane in methanol. Only a small catalytic loading of triton B as small as 1 mol% is enough to finish the reaction. Aromatic, aliphatic, and {alpha},{beta}-unsaturated aldehydes as well as aldehyde hydrates and aqueous aldehydes are successfully employed.