Synthesis of (Bio)-Degradable Poly(β-thioester)s via Amine Catalyzed Thiol-Ene Click Polymerization

The well-known thiol-ene click reaction is used to polymerize dithiols and diacrylate monomers. Using catalytic amounts of hexylamine, poly(ester-sulfide)s are synthesized via consecutive Michael additions between 1,4-butanedithiol and 1,6-hexanediol diacrylate. The molecular weight of the polymers is controlled by the stoichiometric balance of the reagents and by optimizing reaction time. Maximum conversion is achieved at close to 20 min at room temperature. Thermal characterization of the polymer shows a melting temperature of 53 degrees C and good thermal stability of up to 200 degrees C. The poly(beta-thioester) readily degrades when in contact with acetic acid or NaOH solutions, but also degradation under more biological relevant conditions is indicated by partial hydrolysis of the ester linkages in phosphate buffers.