Methylendianiline (MDA) is currently used as a key component of polyimides, epoxy resins, and as a precursor to polyurethanes. Unfortunately, MDA is mutagenic, a potent liver toxicant, and a suspected human carcinogen. As part of a broader effort to address the health impacts of MDA, our group is currently studying bio-derived bisanilines and trisanilines that may serve as replacements for MDA in polymer applications. Recently our group has developed a bisaniline derived from biosynthetic vanillin and a series of trisanilines from resveratrol. Vanillin and resveratrol can be produced on commercial scales from sugar substrates using metabolically engineered yeast. A vanillin derivative, creosol, was efficiently converted to a bisaniline by a sequence that included oxidative coupling, aromatic etherification with 1-fluoro-4-nitrobenzene, and hydrogenation to yield the bisaniline. In addition, two new trisanilines were synthesized from resveratrol and dihydroresveratrol via 3-fold Buchwald-Hartwig aminations with benzophenone imine, followed by hydrolysis with HCl. Polyimide thermosets prepared from these trisanilines had glass transition temperatures above 345 °C, but Ames testing showed that the trisanilines were mutagenic. To address this issue, a third trisaniline was synthesized from resveratrol by a sequence that included hydrogenation, aromatic etherification with 1-fluoro-4-nitrobenzene, and hydrogenation to yield a flexible trisaniline (FTA) with ether linkages. FTA was shown to be non-mutagenic by the Ames test, had no cytotoxicity up to its solubility limit of 10 μg/mL, and aquatic toxicity nearly 140 times lower than that of MDA. The polyimide derived from FTA displayed a Tg of 324 °C and substantially lower pre-cure Tg than the previously studied resveratrol-based polyimides. To further expand on the use of resveratrol as a platform for thermosetting resins, trisepoxides were prepared from resveratrol and dihydroresveratrol and cured with either MDA or FTA to yield epoxy amine networks. These networks had T<sub>g</sub>s up to 290 °C and the network prepared from the unsaturated resveratrol trisepoxide and FTA had a char yield in air of 46%.

High temperature thermosetting polyimide oligomers and epoxy resins derived from biosynthetic vanillin and resveratrol

254th National Meeting (2017)

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