Novel Polyesteramide-Based Diblock Copolymers: Synthesis by Ring-Opening Copolymerization and Characterization

Block copolymers based on a polyesteramide sequence and a polyether block were synthesized in bulk at 250 °C by ring‐opening copolymerization (ROP) of ε‐caprolactone (CLo) and ε‐caprolactam (CLa) as initiated by Jeffamine® M1000, i.e., ω‐NH2 copoly[(ethylene oxide)‐co‐(propylene oxide)] copolymer [P(EO‐co‐PO)‐NH2]. For an initial molar ratio of [CLa]0/[CLo]0 = 1, the copolymerization allowed for the formation of a diblock copolymer with a statistical polyesteramide sequence, as evidenced by 13C NMR. Investigation of the ROP mechanism highlighted that CLo was first polymerized, leading to the formation of a diblock copolymer P(EO‐co‐PO)‐b‐PCLo‐OH, followed by CLa hydrolysis to aminocaproic acid that inserted into the ester bonds of PCLo via aminolysis and subsequent condensation reactions. The outcome is the selective formation of P(EO‐co‐PO)‐b‐P(CLa‐co‐CLo)‐OH diblock copolymers where the composition and length of the polyesteramide sequence can be fine‐tuned by the [CLa]0/[CLo]0 and ([CLa]0 + [CLo]0)/[P(EO‐co‐PO)‐NH2]0 initial molar ratios. The simultaneous copolymerization of ε‐caprolactone (CLo) and ε‐caprolactam (CLa) initiated by an ω‐NH2 macroinitiator was shown to formed a diblock copolymer containing a statistical polyesteramide block, as evidenced by 13C NMR. The lengths of the polyester and polyamide sequences within the polyesteramide block, and so the thermal and mechanical properties of the resulting materials, can be tuned depending on the initial co‐monomer‐to‐amine molar ratio.