1,4-Oxazepan-7-one trifluoroacetate: a modular monomer precursor for the synthesis of functional and biodegradable poly(amino esters)

N-Acylated poly(amino esters) (PAEs) synthesized via organocatalytic ring-opening polymerization (ROP) offer potential for tailored, functional and degradable polymers. In this study, a universal monomer precursor toward N-acylated-1,4-oxazepan-7-ones (OxP)s was synthesized using a three-step approach, allowing for the introduction of various functional groups. Two novel oxidation sensitive OxP monomers bearing a double bond and a sulfide group were designed, as well as two monomers with alkyl moieties. The organocatalytic ROP of the OxP monomers using 1,8-diazabicyclo[5.4.0]undec-7-en (DBU) and 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexyl thiourea (TU) as catalysts was investigated. Polymerizations were performed under ambient temperature, affording homopolymers with narrow dispersities (Ð = 1.09-1.13). As a proof of concept, a post-polymerization thiol-ene functionalization of the allyl functional PAE was performed via photo-rheology experiments. Finally, the (bio)degradability of the N-acylated poly(amino esters) was evaluated through a series of degradation studies under mild enzymatic catalysis, in neutral phosphate-buffered saline solution and under accelerated conditions.