Biodegradable triblock copolymers of PEG, poly(ethyl carbonate) and acidfunctional polycarbonate with precisely controlled molecular weight and well-defined structure were synthesized via organocatalytic living ring opening polymerization, and self-assembled into nanostructures with narrow size distribution. These nanostructures demonstrated exceptionally high loading capacity of an amine-containing cargo (i.e. doxorubicin, an anticancer drug) due to acid base ionic interaction between the cargo and the polymer. To further fine-tune critical properties of drug-loaded micelles, a urea-containing polycarbonate was combined with an acid-functional polycarbonate to form mixed micelles stabilized by hydrogen bonding interactions. The mixed micelles provided greater kinetic stability, nanosize with narrow size distribution and high cargo loading capacity. These nanostructures can be used as carriers to deliver a variety of anticancer drugs that contain amine functional groups. (C) 2010 Elsevier Ltd. All rights reserved.