Probing the Location of the Terminal Groups of Dendrimers in Dilute Solution

The spatial distribution of the terminal groups of poly(amido amine) dendrimers have been determined experimentally by small-angle neutron scattering with deuterium labeling and scattering contrast variation. The radius of gyration of deuterated terminal units of generation 7 dendrimers is 39.3 ± 1.0 Å. This is significantly larger than the radius of gyration of the whole dendrimer, which is 34.4 ± 0.2 Å. These data indicate that dendrimers have terminal groups that are concentrated near the periphery. These results are inconsistent with many computer simulations and some molecular models.