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Research paper : Development of massive synthesis method of organic nanotube toward practical use (M. Asakawa et al.)−172 Synthesiology - English edition Vol.1 No.3 (2009) amphiphilic molecule 2, we departing from our initial plan of using naturally occurring, low-cost materials: the fatty acid raw material for molecule 2, cis-11-octadecenoic acid (cis-vaccenic acid), was expensive at 30,000 yen per gram. In an attempt to further optimize the molecular structure, we found that cis-9-octadecenoic acid (commonly known as oleic acid), which differs from cis-vaccenic acid only in the position of its carbon-carbon double bond, was available from olive oil at low cost; gratifyingly, the organic nanotubes synthesized using the amphiphilic molecule 3 incorporating this fatty acid exhibited its gel-liquid crystal phase transition at a temperature of ca. 70 °C, i.e., it exhibited satisfactory thermal stability (Figure 5).4.2 Self-assembly of organic nanotubesWith the discovery of the amphiphilic molecule 3 that was thermally stable and could be synthesized from naturally occurring, low-cost materials, we set out to investigate an efficient method for the fabrication of organic nanotubes.In the conventional method, organic nanotubes are obtained after heating amphiphilic molecules in water until they dissolve, waiting until the organic nanotubes had formed through self-assembly in solution and precipitation, and then collecting and drying them. There were three problems with this synthetic method: the solubility of the amphiphilic molecule in water was poor; a long time was required for the organic nanotubes to form through self-assembly in solution; and it was difficult to dry the organic nanotubes collected from the solution.To overcome these drawbacks, we investigated the self-assembly of this amphiphilic molecule in other solvents. Indeed, we found that using alcohol as the solvent solved each of these problems; i.e., alcohol dissolved the amphiphilic molecules well, the self-assembly progressed rapidly, and the collected organic nanotubes were readily dried[15].Using this new synthetic method, we could easily synthesize over 100 g of the organic nanotubes in the laboratory, whereas previously it required much effort to produce 1 g (Figure 6).4.3 Utilization development of organic nanotubesOnce we were able to mass-synthesize the organic nanotubes, we conducted a publicity campaign—through press releases and announcements at exhibitions—to attract companies that might have been open to using the material. We made preparations and began to supply samples to various companies in 2007. When providing samples, a material transfer agreement (MTA) was signed between the research institute and each company. The agreement required a specific description of the utilization development and took appropriate measures to understand the fields in which conflicts of interest in intellectual property rights may occur in the future.As result of sample provision, issues in utilization development for different fields became apparent, and we also found that the time required for practical application differed from field to field. Where practical application could be determined quickly, it was important to optimize supply with demand to enable rapid technological transfer.For our own utilization development of the organic nanotubes, our research team investigated (a) the preparation of fluorescent organic nanotubes and (b) methods for the decomposition of organic nanotubes under mild conditions, both useful R&D tools in the field of nanobiology, in addition to studying their dispersibility in water and guest inclusion properties.(a) Development of fluorescent organic nanotubes. This technology involves creating fluorescent organic nanotubes by adding fluorescent molecules during the self-assembly of amphiphilic molecules in organic solution, i.e., during the mass-synthesis of the organic nanotubes (Figure 7). We suspect that these materials will be useful as a research tool for utilization development in the field of nanobiology, where important information can be obtained regarding the stability and behavior of organic nanotubes in vivo through observation of cells tagged with fluorescent organic nanotubes.(b) Method for the decomposition of organic nanotubes. The organic nanotubes form spherical structures when they are heated above their gel-liquid crystal phase transition temperature (ca. 70 °C) in water. While investigating a mild and safe decomposition method, we found that the organic nanotubes transformed into a plate structure when a cyclodextrin solution was added. The tube structure (18)−Fig. 6 SEM image (average exterior diameter: 300 nm; average interior diameter: 90 nm) and a photograph of the organic nanotubes prepared in the form of a white solid power (weight: ca. 140 g).Fig. 7 Cartoon representation of the process used to manufacture fluorescent organic nanotubes.OHHOHOOOHHNOAmphiphilicmoleculeFluorescentmoleculeOrganic solventFluorescentorganic nanotube

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