The clinical success of gene therapy is really dependent on the development of new efficient gene transfer systems. Viral-based gene transfer systems are remarkably efficient in transfecting body cells. However, viral-based systems raised some concerns in terms of immunogenicity, pathogenicity, and oncogenicity. Cationic polymers are promising candidates as they show low host immunogenicity, are cheaper and easier to produce in a large scale than viral ones. However, a crucial question is still pending: which cationic polymer structures and functionalities give the highest transfection efficiency and the lowest cytotoxicity? In dealing with this scientific issue, new cationic polymers with key structural parameters and functionalities were developped during this PhD thesis. The key structural features studied are : (i) pH sensitive primary and tertiary amine entities for DNA complexation and to ensure the endosomal escape, (ii) an alkyne group to attach ligands capable to target specific cell membrane receptors for an efficient cell recognition and receptor-mediated cellularuptake, (iii) “charge-shifting” amino-based polyacrylates for DNA release and to decrease cytotoxicity and (iv) PEG chains (PEGylation) to achieve high stability, longer circulation in physiological conditions and a better biocompatibility. The synthesis of such multi-structural cationic polymers has been achieved through the combination of RAFT polymerization and thiol-yne click coupling reaction. The structure/complexation and the structure/cells viability relationships have been investigated during this work.