Hisayuki Watanabe

Mixing induced thixotropy of a two-component system of alkylurea organogelators having different alkyl chains

Mixing induced thixotropy was demonstrated on a two-component system of alkylurea with different alkyl chains known as low-molecular-weight organogelators. Individually, the component gels did not show thixotropic behavior. The improved network structure obtained by mixing might enable enhanced toughness and stimulus-responsiveness of mixed gels.

Synthesis of a new squarylium alkylamide family and its organogelation ability

A new family of squarylium monoalkylamides and dialkylamides was synthesised and its organogelation ability was evaluated. We found that both squarylium monoalkylamides and dialkylamides formed organogels in DMF. We also found that ion-selective organogel formation was observed in DMF solutions containing metal ions, and gel electrolytes consisting of squarylium alkylamides, DMF and LiClO4 showed good ionic conductivities comparable to that of the corresponding liquid electrolytes.

Long-chain alkylamide-derived oil gels: mixing induced onset of thixotropy and application in sustained drug release

We showed that the gelation ability of commercially available long-chain alkylamides, behenamide (BAm) and erucamide (EAm) in various solvents for the first time. Furthermore, oil gels derived from mixtures of BAm and EAm exhibited thixotropic properties although the same property was absent in the oil gels prepared separately using each alkylamide. The thixotropic behaviour of a two-component mixed gel was evaluated using a rheometer quantitatively. We also found that the obtained two-component oil gel can be formulated for use as a vehicle for sustained drug release. The drug, antipyrine, in BAm/EAm (1/1, w/w) olive oil gel formulation was gradually released into water following Fickian diffusion kinetics.

Creation of thixotropic multicomponent alkylamide organogels containing non-volatile oil as potential drug release host materials

Multicomponent alkylamide organogels containing non-volatile oils were generated as potential thixotropic host materials for medicinal applications such as ointments. In the presence of these non-volatile oils, a three-component alkyl amide system exhibited mixed induced thixotropy. This thixotropic organogel showed drug release abilities following diffusion kinetics and may be suitable drug release host materials.

Improved mechanical properties of alkylamide organogels via a mixing enhancement effect

Mixtures of alkylamide derivatives with different alkyl chains were found to form organogels which exhibit thixotropic properties, while single alkylamide components formed organogels which did not exhibit such properties. With a three-component alkylamide system, the transparency and mechanical properties (toughness and stimulus-responsiveness) of the resulting organogels were enhanced. This mixing enhancement for organogelators may be due to the improved network density compared with that of the one-component systems.

Onset of mixing-induced thixotropy in hydrogels by mixing two homologues of low-molecular-weight hydrogelators

We determined the onset of thixotropy in hydrogels when two homologues of low-molecular-weight hydrogelators, N-alkyl-D-glucamides, were mixed. Intriguingly, the hydrogels generated from the individual components did not show such behaviour. The mixing induced onset of thixotropy might be attributed to the improved network quality.

A new composite thixotropic hydrogel composed of a low-molecular-weight hydrogelator and a nanosheet

A two-component composite comprised of a low-molecular-weight hydrogelator and the nanosheet Laponite®, a synthetic layered silicate, showed thixotropic behaviour, whereas each single component did not show thixotropic behaviour at the same concentration. This mixing enhancement effect may be attributed to the improved quality of the gel network.

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.

N-Alkylamido-D-glucamine-based gelators for the generation of thixotropic gels

Hydrogels made from new gelators, composed of the alkyl chain and a D-glucamine moiety linked together with glycine(s), exhibit thixotropic properties, whereas the hydrogels formed with structurally similar N-alkyl-D-glucamide, which do not contain the glycine moiety, have a tendency to crystallize and do not show thixotropic behaviour.

A new water-soluble aromatic polyamide hydrogelator with thixotropic properties

The water-soluble aromatic polyamide poly(3-sodium sulfo-p-phenylene terephthalamide) forms a hydrogel with anisotropy, which exhibits good thixotropic behaviour, even at the critical gel concentration of the gelator (1.0 wt%).