Dynamical dimer structure and liquid structure of fatty acids in their binary liquid mixture: decanoic/octadecanoic acid and decanoic/dodecanoic acid systems |
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Authors: | Iwahashi Makio Takebayashi Shintaro Taguchi Masakazu Kasahara Yasutoshi Minami Hideyuki Matsuzawa Hideyo |
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Institution: | School of Science, Kitasato University, 1-15-1 Kitasato, Sagamihara 228-8555, Japan. maki@kitasato-u.ac.jp |
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Abstract: | Dimer structure and liquid structure of fatty acids in their binary mixtures such as decanoic acid (DA)/octadecanoic acid (SA) and DA/dodecanoic acid (LA) were studied through the measurements of self-diffusion coefficient (D), differential scanning calorimetry (DSC), density and viscosity. The obtained phase diagrams showed that DA and SA form a eutectic in the solid state but partly a solid solution in the SA-rich region; DA and LA form an incongruent-melting compound which forms a eutectic with DA. In the liquid mixture of DA and SA, the D of DA is larger than that of SA over the entire range of compositions and tends to approach the D of SA with increasing SA-mole fraction; the D of DA in the DA/LA system is also larger than that of LA especially in the LA-poor region and steeply approaches that of LA with increasing LA-mole fraction. These D values and phase diagrams were compared with those for the binary mixtures of n-alkanes (C14/C20, C19/C20 and C20/C24); it is concluded that the two kinds of fatty acids always form their individual homodimers in their liquid mixtures regardless of their compositions and temperatures. |
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Keywords: | Decanoic acid Dodecanoic acid Octadecanoic acid Dimer structure of fatty acid Liquid structure of fatty acid Self-diffusion coefficient |
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