Starch-Reinforced Vinylogous Urethane Vitrimer Composites: An Approach to Biobased, Reprocessable, and Biodegradable Materials

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.

Exchangeable disulfide bond containing highly flexible epoxy vitrimers with shape‐memory, self‐healing, and UV shielding attributes

“…Over the last few years, fossil resources are seriously in danger of running out due to the population boom and the massive consumption of resources to produce non‐renewable materials. As a result, many biobased sustainable, and nontoxic resources have been exploited as substitutes for petroleum‐based feedstocks 19 . Among the commercially available epoxy, the most popular one is DGEBA which occupies approximately 90% of the total production of epoxy thermoset 20 .…”

Biodegradable Polyester-Based Vitrimers Exhibiting Transesterification-Induced Topography Isomerization under Recycling

“…The biodegradability of the vitrimers in seawater was demonstrated to be comparable to that observed with the ESO raw material. Other biomass raw materials, including oxidized starch, 33 oil natural corn starch, 34 and divanillic acid, 26 have also been employed in the preparation of biodegradable vitrimers. Recent publications reported the utilization of artificial biodegradable polymers as precursors in the preparation of biodegradable vitrimers.…”

An effective approach for the preparation of epoxy vitrimers by in situ formation of dynamic and permanent linkages in a one-pot curing reaction

“…Based on their unique and attractive properties, vitrimers have received much research attention and significant progress has been made in recent years, 8 including catalyst-free systems, 9,10 biomass-based vitrimers, 11,12 vitrimers based on various dynamic covalent bonds, 13,14 integration of vitrimer features into conventional polymers, 15,16 and vitrimer-based organic–inorganic composites. 17,18…”

“…Based on their unique and attractive properties, vitrimers have received much research attention and significant progress has been made in recent years, 8 including catalystfree systems, 9,10 biomass-based vitrimers, 11,12 vitrimers based on various dynamic covalent bonds, 13,14 integration of vitrimer features into conventional polymers, 15,16 and vitrimer-based organic-inorganic composites. 17,18 Conventional thermosetting resins, such as epoxy resins, are prepared by a step-growth polymerization employing multifunctional small molecular monomers at high reaction conversions. Dynamic covalent bonds could be introduced to the crosslinked networks via in situ crosslinking reactions, such as the carboxylic anhydride cured epoxy and carboxylic acid cured epoxy systems, which resulted in epoxy resin vitrimers possessing dynamic ester bonds.…”