Star polymers (SPs) containing a hyperbranched poly(ethylene imine) (PEI; number-average molecular weight = 10,000) core and polylactide arms were synthesized via the ring-opening polymerization of lactide. PEI was used as a multifunctional macroinitiator for the ring-opening polymerization of lactide. Different lactide monomer/amino-functional group (LA/NHn; n = 1 or 2) ratios were used for preparing SPs with different molecular weights. SPs were able to encapsulate small guest molecules such as Rose Bengal; they also transported small, hydrophilic molecules from water to the organic phase. The transport capacity of all the nanocarriers depended on the LA/NHn ratio used for synthesizing the SPs. Nanocarriers with a higher LA/NHn ratio had higher transport capacities. The size of all the nanocarriers depended on the type of solvent. In chloroform, these nanoparticles had several sizes that were related to the self-assembly of these nanocarriers, but in acetone, they were monodisperse, and their size was smaller than that in chloroform. Also, the transport of polar dyes from water to the chloroform phase was possible. (c) 2006 Wiley Periodicals, Inc.