Organocatalytic Ring-Opening Polymerization of -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 -acylated-1,4-oxazepan-7-one (OxP) monomers, produced from -acylated-4-piperidones using the Baeyer-Villiger oxidation reaction. The ROP of OxPs, conducted in CHCl 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 -acylated substituent of monomers, with the following reactivity order: OxP > OxP > OxP > OxP. 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(-acylated-1,4-oxazepan-7-one) (POxP) polymers are amorphous with different glass transition temperatures (), depending on the -acylated substituent (: -2.90 to 43.75 °C). Among the synthesized polymers, only POxP was water-soluble and it degraded much faster than polycaprolactone in an aqueous phosphate buffer saline solution (pH = 7.4). Therefore, poly(-acylated-1,4-oxazepan-7-one)s are potential biodegradable alternatives to poly(2-oxazoline)s.