A novel series of imidazolium quaternized polymers based on poly(chloromethyl styrene) has been designed and synthesized, using nitroxide mediated polymerization and post‐polymerization functionalization. They are characterized by ATR‐FTIR (attenuated total reflectance‐Fourier transform infrared spectra) and 1H NMR in terms of functional groups and composition, which indicate the success of the synthetic scheme utilized. The solution behavior of the quaternized polymers has been investigated in water, phosphate buffer saline (PBS), and PBS(90%)‐FBS(10%) (fetal bovine serum) by static, dynamic, and electrophoretic light scattering. The functionalized polymers have been studied in terms of structure and stability during changes in temperature and ionic strength of their aqueous solutions. The copolymers form stable aggregates with positive surface charge. All cationic polymers are found to interact extensively with DNA via electrostatic interactions, forming stable complexes at certain ratios of the components.