Binding of carboxylated starburst dendrimers to poly(diallydimethylammonium chloride)

The interaction between poly(diallydimethylammonium chloride) (PDADMAC) and carboxylated starburst dendrimers (generations 0.5, 3.5, 5.5 and 7.5) was investigated over a range of ionic strength from 0.01 to 0.50 M NaCl using pH titration, turbidimetry and quasi-elastic light scattering methods. Complex formation occurs most readily with generation 7.5, which may be attributed to its high charge density relative to the smaller dendrimers. The effects of ionic strength confirmed the electrostatic nature of the interaction, while pH titrations revealed that complex formation is stoichiometric. Analysis of pH titrations via the effect of binding on the pK(a) of the dendrimer carboxylic acid groups lead to estimates of the free energy of complex formation.