Synthesis and characterization of novel poly(α-methyl β-alanine-b-lactone)s through hydrogen-transfer and ring-opening polymerization

A series of novel poly(α-methyl β-alanine-b-lactone)s were prepared by a combination of hydrogen-transfer polymerization (HTP) of methacrylamide (MAm) and anionic ring-opening polymerization (AROP) of β-propiolactone (BPL), β-butyrolactone (BBL), and δ-valerolactone (DVL). For this purpose, poly(α-methyl β-alanine) (PmBA) having a living anionic end-group for a further extension was obtained via HTP of MAm. The anionic end-group on PmBA chains were used as initiation sites for AROP of BPL, BBL, and DVL. Fourier Transform Infrared Spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance Spectroscopy (¹H-NMR) confirmed the existence of both ester and α-methyl β-alanine (mBA) units in the final products. MALDI-MS analysis revealed that the poly(α-methyl β-alanine-b-lactone)s with average molar masses of several thousand g·mol⁻¹ were obtained. DSC and TGA thermograms of each copolymer showed that the copolymers comprised the mBA and the corresponding ester units.