Kinetics of Complex Formation between DNA and Cationically Charged Cylindrical Brush Polymers Observed by Stopped Flow Light Scattering

The complex formation of pUC19 DNA and a cylindrical brush polymer with quaternized poly(vinyl pyridinium) side chains is investigated by stopped flow light scattering (LS). In highly dilute solutions up to two kinetic processes are observable, depending on the mole fraction of anionic charges, chi(anion). For chi(anion) < 0.2 and chi(anion) > 0.4-0.5 only one kinetic process was identified leading to the largest complexes at chi(anion) = 0.4 well below charge stoichiometry. For 0.2 < chi(anion) < 0.4 two kinetic growth processes were identified: The initially formed complexes on the time scale of a few hundred milliseconds keep growing by an unusual fractal growth process until after several minutes they become stable. This last fractal process does not follow the classical Smoluchowski coagulation theory as monitored by LS up to 90 s after mixing.