Publications

Neutron spin-echo (NSE) experiments were performed at room temperature on D2O solutions of fifth generation poly(amido amine) (PAMAM) dendrimers with different types of end groups. Intermediate correlation functions I(Q,t)/I(Q,0) at different scattering vectors Q as a function of time t show different dynamics for dendrimer concentrations of 1.0 and 10 wt %, while the dynamics was independent of the chemical species of the end groups, hydroxyl or glucopeptide. The NSE results for a 10 wt % solution followed a single-exponential decay. With increasing Q, the evaluated effective diffusion coefficients D-eff decreased and converged to the translational diffusion coefficient D-0, which was obtained from dynamic light scattering. It is assumed that the Q-dependence of D-eff is caused by the dendrimer-dendrimer interaction, which is observed as the inter-dendrimer structure factor on small-angle neutron scattering. On the other hand, NSE results for a 1.0 wt % solution were well-fitted to a double-exponential function with two decay rates (fast and slow modes). It was observed that the diffusion coefficient of the slow mode corresponds to D-0. The fast mode originates from the motion of amido-amine segments in the dendrimer, which is a common internal unit for the two dendrimers.