4-Aminocinnamic acid derived from microbial resources must be one of the most expected monomers for application in high-performance bio-plastics. Especially, a bio-based polyamide which had been synthesized by 4-aminocinnamic acid derivatives showed high mechanical strengths as high-transparent plastics. Moreover, the mechanical strengths were enhanced by the addition of adipic acid as a third monomer to synthesize co-polyamide. Significantly, strain energy density of this co-polyamide was also enhanced by the addition of adipic acid which probably affects both flexibility and strength of co-polyamide. However, there still have the possibilities to improve these mechanical properties by controlling the selection of third monomers and of their composition ratio. Moreover, the structural advantages of that co-polyamide were not clear so far. From above, we focused on the mechanical properties of a series of co-polyamides which had been synthesized by 4-aminocinnamic acid derivatives and various kinds of aliphatic dicarboxylic acids with controlling their composition ratio. Additionally, structural analyses of these co-polyamides were carried out by means of FT-IR and other analysis methodologies. As a result, obtained co-polyamide showed higher elongation at break (140 % at max) and strain energy density (250 MJ/m<sup>3</sup> at max) which contained higher ratio of aliphatic dicarboxylic acids. The maximum mechanical strength was about 530 MPa when pimelic acid (C=7) was contained with 25 mol%, which was 60 MPa higher than that of reported co-polyamide in our research group. Furthermore, the result of <i>in-situ</i> FT-IR measurement indicated tautomerization throughout tensile test. From this tautomerization, the cyclobutene rings in the co-polyamides were deformed from V-shaped non-plain structure to plain one, which reduces stress concentration in main-chain throughout tensile test.

Structure-property relationships of bio-based polyamides with super-high mechanical toughness

255th National Meeting (2018)

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