Synthesis of A2+B3 type hyperbranched poly(amide-ether) block copolymer and its shape memory function

Abstract

High-molecular-weight hyperbranched polyether-b-amides (hb-PEBA; number average molecular weight (Mn) = 29.2–96.2 kDa) were successfully prepared by polycondensation of NH2-terminated poly(ethylene oxide) (PEO; Mn = 3.35, 4.6, 8.0, and 10.0 kDa) as A2-type and COOH-terminated three-armed N-methylbenzamide pentamers (TMA-3MAB5) as B3-type macromonomers in N-methylpyrrolidone (NMP) at 35–60 °C for 6 h. TMA-3MAB5 was prepared by stepwise condensation of 4-N-methylaminobenzoic acid (MAB), trimesic acid (TMA), and thionyl chloride/NMP as the building block, core molecule, and condensation reagent, respectively. Transparent to opaque films were prepared from all polymer samples through the solvent casting method using CHCl3, and the crystallization of PEO segments (crystallization degree Xc 15%–66%) was confirmed using differential scanning calorimetry (DSC). The hb-PEBA films showed tensile strengths of 0.71–16.8 MPa, with breaking elongation of 40–350%, and tensile elastic moduli of 0.10–1.43 GPa, depending on Mn and polymer composition. The superior shape memory properties of hb-PEBA polymers compared with their linear counterparts were confirmed by deformation at 80 °C, shape retention (memory) at room temperature, and shape recovery by reheating. Overall, the well-controlled TMA-3MAB5 was undoubtedly effective for the synthesis of high Mnhb-PEBA, resulting in improved mechanical and shape memory properties.