New star shaped block copolymers were synthesized according to a core first strategy, with a hydrophobic polytetrahydrofuran (PTHF) central block and a poly(2-methyl-2-oxazoline) (PMeOx) external block. First, the cationic polymerization of THF was initiated from a tetrafunctional triflate ester synthesized in situ. The chain ends were functionalized by quenching the polymerization with an excess of MeOx, that allowed for the MeOx polymerization under microwave in a subsequent step. Demonstration of the expected structures was carried out at each step of the polymerization. The controlled molar mass of the star copolymers was kept below 5000 g mol À1 in order to mimick the structure of the efficient poloxamines for gene transfer applications. Formulations containing various concentrations of star block copolymers were intramuscularly injected in mice. Efficient gene transfer was measured at formulations with very low concentration of copolymer compared to reference standard containing Lutrol Ò .