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Research paper : Development of massive synthesis method of organic nanotube toward practical use (M. Asakawa et al.)−170 Synthesiology - English edition Vol.1 No.3 (2009) of carbon nanotubes—they have not been put to practical use, primarily because organic nanotubes have been difficult to mass-produce successfully, unlike carbon nanotubes; therefore, relatively little research has been performed into the practical applications of organic nanotubes or into comparisons with existing materials. Resolving this issue would make it possible to verify the potential of using organic nanotubes as materials for its practical applications.The objective of this study was to create a new industry involving the practical use of organic nanotubes. To do so, a mandatory requirement was the development of a method for the mass synthesis of organic nanotubes. Also, it was necessary for us to develop low-cost molecules for the synthesis of the organic nanotubes, to perform utilization development, and to demonstrate their safety.2 Goals and scenario to achieve the goalFor the practical application of organic nanotubes, it is necessary for companies to actually use these materials in trial runs so that they can be accepted as candidates for product development. To promote trial use by companies, it was necessary to develop a mass synthesis method that enables a steady sample supply and provides functions that can be employed in various fields, while fulfilling such practical considerations as cost competitiveness and safety. Thus, it was necessary to determine an optimal molecular structure for organic nanotube synthesis through molecular design and synthesis and then to produce a low-cost molecule by simplifying the synthetic process to cut costs. Also, it was important to lower the entry barrier for industrial use by conducting a safety assessment and sharing the information (Figure 3).To achieve the aforementioned goals, we first developed a molecular design and synthesis technology using amphiphilic molecules for the fabrication of organic nanotubes with considerations of economy, safety, and mass production. The policy we employed for molecular design was to use a material resource that was recyclable, naturally occurring, and abundant (i.e., available at low cost from a reagent supplier). We established a working hypothesis that amphiphilic molecules synthesized from naturally occurring raw materials would be safe.Next, we developed a process—an improvement of the established self-assembly method—to enable the mass synthesis of organic nanotubes from amphiphilic molecules. We optimized four phases of the organic nanotube synthesis to increase efficiency and enable mass production: (i) dissolving the amphiphilic molecule in a solvent; (ii) forming organic nanotubes through self-assembly of amphiphilic molecules; (iii) separating the organic nanotubes from the solvent; and (iv) drying the organic nanotubes. Not only would the development of a suitable large-scale synthesis enable both economy and mass production, it would also open up the possibility of developing organic nanotubes in various fields—where investigations have previously been limited by insufficient amounts of materials (e.g., 100 mg or less)[11]—and enabling appropriate safety assessments.Third, for the practical application of organic nanotubes in various fields, it was important to recognize their superiority through comparisons with the properties of conventional materials. For utilization development, it is important that companies use the materials in trials to determine whether they can be applied in actual situations. Therefore, it was necessary for us to provide companies developing conventional materials with organic nanotubes and to demonstrate the efficacy of organic nanotubes through joint research opportunities. To encourage the companies to experiment with the materials, we undertook an active promotion campaign, presenting organic nanotube technology at conferences and exhibitions.Finally, because organic nanotubes are new materials, we knew that they would not be accepted in society unless their safety was established—even if their effectiveness was recognized for utilization development[12]. Therefore, we conducted safety assessments of the amphiphilic molecules and organic nanotubes that we synthesized from naturally occurring raw materials. We shared this safety information with relevant companies to lower the entry barrier for this technology.To satisfy the first and second phases of the scenario, it was necessary for us to conduct several tasks simultaneously. Because organic nanotubes exist in the field of supramolecular chemistry, which studies molecules as component units and investigates their assembly functions based on interactions with other molecules, we developed our molecular design, synthesis, and self-assembly methods by carefully investigating the molecular structure and its potential for self-assembly.The third phase of scenario was to be investigated after completing the first and second phases. Because heteronomous factors had to be solved by comparing the third phase with first and second phases, organized and strategic efforts were necessary for rapid assessment.(16)−Fig. 3 Schematic representation of the development and application scenario.CostSafetyDesignandsynthesisVolumePractical use of organic nanotubesUtilization developmentSafety assessment

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