Bis-spirocyclic diol monomers and polyurethanes derived from citric acid: Synthesis, properties, electrospinnability, and evaluation of chemical recyclability

• Citric acid derived spiro-ketal diol monomers afforded thermoplastic and amorphous polyurethanes (PU-s) • PU-s are transparent and show T g -s up to 145 °C and T d -s up to 309 °C. • Electrospinning afforded smooth fiber mats. • Ketal groups can be selectively hydrolyzed for the chemical recycling of these polymers. A series of rigid spiro-acetal-containing diol monomers derived from citric acid were synthesized and reacted with five different diisocyanates to form partially biobased thermoplastic polyurethanes (PUs) with different chemical and physical properties. The PUs had a renewable carbon content between 48 and 71 %, and all formed transparent and colorless films with glass-transition temperatures between 48 and 145 °C, and thermal stability at least up to 254 °C. Copolymers with polytetrahydrofuran were also prepared to further expand the range of properties. The PUs showed good electrospinnability, and electrospun fiber mats exhibited a maximum stress of 11.5 MPa and strain of ca. 47 %. Hydrolytic degradation studies indicated that the acetal-functional groups in PUs were selectively and efficiently hydrolyzed in acidic aqueous acetone or DMSO, as well as under mechanochemical treatment. This indicated possible chemical recycling pathways of this new family of versatile polymer materials.