THE AMPHIPHILIC MULTIARM COPOLYMERS BASED ON HYPERBRANCHED POLYESTER AND LYSINE: SYNTHESIS AND SELF-ASSEMBLY

The amphiphilic multiarm copolymers were synthesized through the modification of commercially available hyperbranched polyesters (Boltorn H40) with N-epsilon-carbobenzoxy-L-Lysine N-carboxyanhydride (ZLys-NCA). After being condensed with N-Boc-phenylalanine (Boc-(N)Phe) and deprotected the Boc-groups in trifluoroacetic acid (TFA), the original terminal hydroxyl groups were transformed into the amino groups and then initiated the ring-opening polymerization of ZLys-NCA. The hydrophilic poly(L-lysine) was grafted to the surface of Boltorn H40 successfully after the protecting benzyl groups were removed by the HBr solution in glacial acetic acid (33 wt%). The resulting multiarm copolymers were characterized by the H-1-NMR, GPC and FTIR. The arm length calculated by NMR and GPC analysis was about 3 and 13 lysine-units for H40-Phe-PLys1 and H40-Phe-PLys2 respectively. Due to the amphiphilic molecular structure, they displayed ability to self-assemble into spherical micelles in aqueous solution with the average diameter in the range from 70 nm to 250 nm. The CMC of H40-Phe-PLys1 and H40-Phe-PLys2 was 0.013 mg/mL and 0.028 mg/mL, respectively, indicating that H40-Phe-PLys1 with shorter arm length is easier to self-assemble than H40-Phe-PLys2 with longer arm length.