Organocatalytic Ring-Opening Polymerization of N -Acylated-1,4-oxazepan-7-ones Toward Well-Defined Poly(ester amide)s: Biodegradable Alternatives to Poly(2-oxazoline)s.

We report a series of poly(ester amide)s (PEAs) synthesized by organocatalytic ring-opening polymerization (ROP) of N -acylated-1,4-oxazepan-7-one (OxP) monomers, produced from N -acylated-4-piperidones using the Baeyer-Villiger oxidation reaction. The ROP of OxPs, conducted in CH 2 Cl 2 at room temperature with benzyl alcohol as initiator and TBD/TU (1,5,7-triazabicyclo[4.4.0]dec-5-ene/thiourea) as a binary organocatalytic system, revealed a controlled/living character. The thermodynamics of the ROP highly depends on the N -acylated substituent of monomers, with the following reactivity order: OxP Ph > OxP Me > OxP Pr > OxP Bn . Based on NMR results, it seems that our system follows the hydrogen bonding bifunctional activation mechanism. All intermediates and final products were characterized by NMR, MALDI-TOF MS, SEC, and DSC techniques. All poly( N -acylated-1,4-oxazepan-7-one) (POxP) polymers are amorphous with different glass transition temperatures ( T g ), depending on the N -acylated substituent ( T g : -2.90 to 43.75 °C). Among the synthesized polymers, only POxP Me was water-soluble and it degraded much faster than polycaprolactone in an aqueous phosphate buffer saline solution (pH = 7.4). Therefore, poly( N -acylated-1,4-oxazepan-7-one)s are potential biodegradable alternatives to poly(2-oxazoline)s.