Designed amino acid-based deep eutectic solvents as a platform to functionalize biomedical elastomers by polyaddition reactions

In the production of synthetic polymer materials containing amino acids (AA) segments, dispersion of the AA monomer is a major hurdle. Because of high monomer cohesive energies, dispersion requires highly polar solvents, complex chemical syntheses, and long reaction times. Herein, we report a robust method for the facile preparation of biomedical thermoplastic elastomers under solvent-free conditions. This method employs an amino acid-based deep eutectic solvent (AADES) as the polymerization platform to allow AA liquefaction and polymerization after AA deprotonation. The AA molecules in the stabilized AADES accounted for a mass fraction of up to 68 %, and the mass fraction of the AA chain segments in the elastomer main chain was higher than 11.2 %. In addition, the tensile strength of the elastomer obtained by AADES with further chain extension reached 26 MPa, and the elongation at break reached 555 %. The broad scope and functional group tolerance of the method were demonstrated by the facile synthesis of polyurethane elastomer chain extended by different types of AADES, including AA with low-reactivity functional groups such as guanidine, tertiary amine, and sulfhydryl. The mechanisms of AADES formation and elastomer polymerization were demonstrated using L-lysine (Lys), a common chain extender. By dissolving quaternary ammonium salts (QAS) in AADES to further endow the elastomers with antimicrobial properties, the prepared elastomers are expected to contribute to tissue repair. Overall, our strategy holds great potential for facilitating the synthesis of biomedical polymer materials containing AA segments and expanding their applications in tissue engineering.