AFM studies of high-generation PAMAM dendrimers at the liquid/solid interface

The structural distortion of high-generation poly(amidoamine) (PAMAM) dendrimers at the liquid/solid interface was investigated in situ using tapping mode atomic force microscopy (AFM). With a substantial compression along the surface normal but minor lateral expansion, isolated PAMAM dendrimers at the water/mica interface exhibit dimensions similar to those reported for the same species in dense, dried arrays, rather than those of isolated, dried units. On graphite substrates, adsorbed dendrimers exhibit weaker adhesion forces than on mica. AFM images of lower generation dendrimers at the water/graphite interface reveal additional features interpreted as large three-dimensional aggregates.