Abstract
Vitrimers represent permanent and dynamic polymer networks at the same time. The combination of dynamic covalent bonds and widely available, biodegradable, and biobased raw materials enables new polymers with an excellent carbon footprint, mechanical properties, and outstanding features in terms of multiple recycling methods, e.g., thermomechanical, chemical, and biological reprocessing/reusability. Natural corn starch granules have been surface-modified by an acetoacetylation reaction without using any additional solvent and maintaining the inner semicrystalline structure, giving a polyfunctional cross-linker for starch-reinforced vitrimer composites. Vinylogous urethane vitrimer matrices were synthesized by the condensation reaction of fully acetoacetylated glycerol and different diamines, while glycerol and the diamines were deliberately selected as potentially biobased raw materials. Seven different matrix vitrimers were synthesized with a content of 0–70 wt % of modified starch and investigated in terms of their thermal and mechanical properties. In total, 20 elastomeric and thermosetting materials have been prepared, exhibiting high elastic moduli of 2 GPa with short stress relaxation times and a high content of modified starch up to 70 wt %. The composites show low swelling ratios, suppressing the natural gelatinization of starch in water. Moreover, suitable thermomechanical, chemical, and enzymatic recycling methods for closed-loop cycles, remolding, reusability, and biodegradability were developed.
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