Multi‐arm star block copolymers based on ε‐caprolactone with hyperbranched polyglycerol core

Multi‐arm star block copolymers based on ε‐caprolactone have been prepared by a core‐first approach using propoxylated hyperbranched polyglycerol P(G₅₂PO₃) as a polyfunctional initiator. Various monomer/initiator ratios were employed in the Sn‐catalyzed polymerization in order to vary the length of the caprolactone arms (DP_n(arm) = 10 to 50). The molecular weights of the block copolymers were in good aggreement with the calculated values. Careful NMR analysis revealed that the monomer/initiator ratio not only controls the arm length, but also influences the degree of functionalization. Poly(ε‐CL) stars with 52 arms and absolute molecular weights between 69 200 and 360 400 g/mol have been prepared. SEC measurements showed that the narrow polydispersity of the core molecule (M_w/M_n = 1.24) could be maintained upon block copolymerization. The resulting star polymers exhibited polydispersities between 1.21 and 1.33.