STRUCTURAL-PROPERTIES OF METHANOL-POLYAMIDOAMINE DENDRIMER SOLUTIONS

We used small angle x-ray scattering to study interparticle structural properties of polyamidoamine starburst dendrimers (PAMAM, with an eth ylenediamine central core) in methanol solutions. We have explored the intensity profiles for solutions of starburst of different generation s (g = 2, 3.5, 4) at various concentrations. We find from the measured spectra that the half-integer generation, g=3.5, is characterized by pronounced interparticle correlations also in the very dilute regime. By means of a simple statistical-mechanical model, widely used in char ged complex fluids (proteins and ionic micellar solutions), we calcula te in this latter case the dendrimer-dendrimer structure factor S(q). The results obtained give clear indication of a partial ionization pro cess which involves the carboxylate (COO-Na+) terminal groups of the d endrimer. The calculated macroion charge number, independent of the so lution concentration, is Z(0)similar or equal to 6. [S1063-651X(98)091 11-9].