Biobased Amide Bis-Benzoxazines Enable Tunable, Reprocessable Benzoxazine/Polyether Diamine Vitrimers

We introduce a novel bis-biobased benzoxazine monomer, PAHDA-fa, which is 95% biobased and features amide groups, yielding a vitrimer by copolymerization with polyether diamine. The monomer is synthesized via a straightforward, green, and workup-free two-step route using phloretic acid, hexamethylene diamine, and furfurylamine. Following copolymerization with polyether diamine (PEA, Mn 600 g/mol), robust cross-linked vitrimer networks are obtained, with properties adjustable from thermoset- to elastomer-like by varying the benzoxazine/amine ratio. Comprehensive spectroscopic, thermal, and extraction analyses confirm efficient polymerization and a high degree of cross-linking (gel content = 72–97%), alongside an excellent thermal decomposition temperature (T5% = 260–270 °C). The resulting materials display glass transition temperatures Tg of −17 to 72 °C with decreasing amine content in the corresponding polyBZ. The vitrimeric nature is evidenced by Arrhenius-like stress relaxation (Ea = 118–122 kJ/mol), topology freezing temperature Tv of 72 to 79 °C, and rapid relaxation times of 34 to 64 s at 180 °C with decreasing amine content. Notably, these samples are physically recyclable via thermal reprocessing over multiple cycles without loss of performance. This study advances the development of sustainable benzoxazine/amine vitrimers based on green chemistry.