Characteristics of polymer forming poly( isobutylcyanoacrylate) (PIBCA) nanoparticles used as drug delivery systems were investigated. The nanoparticles were prepared by emulsion polymerization of IBCA in the presence of dextran by either anionic or redox radical emulsion polymerization. These methods allowed complete polymerization of IBCA. The nanoparticles were formed by heterogeneous polymers. Characterization of PIBCA and dextran parts after selective hydrolysis of the counterpart highlighted differences in term of composition and structure of polymer. The anionic emulsion polymerization (AEP) led to the simultaneous formation of homopolymer of PIBCA and of copolymers of several short PIBCA chains grafted on a dextran chain. In redox radical emulsion polymerization (RREP), nanoparticles contained only copolymers with bloc structure in which PIBCA chains exhibited a high molecular weight and a broad distribution. These results confirmed hypothesis on formation of diblock copolymers by RREP and of grafted copolymers by AEP.