The amphiphilic multiarm copolymers were synthesized through the modification of commercially available hyperbranched polyesters (Boltorn H40) with

N

-

ε

-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

1

H-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.