Due to the depletion of fossil fuels, higher oil prices, and greenhouse gas emissions, the scientific community has been conducting an ongoing search for viable renewable alternatives to petroleum-based products, with the anticipation of increased adaptation in the coming years. New academic and industrial developments have encouraged the utilization of renewable resources for the development of ecofriendly and sustainable materials, and here, we focus on those advances that impact polyurethane (PU) materials. Vegetable oils, algae oils, and polysaccharides are included among the major renewable resources that have supported the development of sustainable PU precursors to date. Renewable feedstocks such as algae have the benefit of requiring only sunshine, carbon dioxide, and trace minerals to generate a sustainable biomass source, offering an improved carbon footprint to lessen environmental impacts. Incorporation of renewable content into commercially viable polymer materials, particularly PUs, has increasing and realistic potential. Biobased polyols can currently be purchased, and the potential to expand into new monomers offers exciting possibilities for new product development. This Review highlights the latest developments in PU chemistry from renewable raw materials, as well as the various biological precursors being employed in the synthesis of thermoset and thermoplastic PUs. We also provide an overview of literature reports that focus on biobased polyols and isocyanates, the two major precursors to PUs.

Diisocyanates used in polyurethanes are commonly prepared by phosgenation of petroleum-sourced diamines. This involves highly toxic phosgene and produces corrosive HCl, limiting synthetic applications. In our search for a renewable source for diisocyanates, we have developed a practical methodology for the production of isocyanates from algae-biomass-derived fatty acids or other renewable sources. This technique utilizes flow chemistry to prepare and convert high-energy intermediates, thus mitigating safety concerns. By the use of continuous flow, acyl azides are prepared from hydrazides and subsequently heated to undergo Curtius rearrangement, affording isocyanates in one scalable process. The method is efficient, safe, and sustainable, offers an opportunity to prepare isocyanates and diisocyanates from renewable feedstocks, and is amenable to distributed manufacturing processes.

To achieve sustainably-sourced polymers from algae, azelaic acid was prepared from an algae oil waste stream and converted into a flexible polyurethane foam. The heptanoic acid co-product was converted into both a flavoring and a renewable solvent.