Segmental contrast of dendrimers:: a small-angle neutron scattering study including contrast variation

We present an analysis of the distribution of endgroups within a urea-functionalized poly(propyleneamine)-dendrimer of 4th generation by small-angle neutron scattering (SANS). The contrast between the solute and the solvent is varied in a systematic fashion (contrast variation). The analysis of the scattering intensity corrected for incoherent contributions gives three partial scattering functions that depend differently on contrast. It is demonstrated that difference in contrast of the different segments of the molecules give an additional scattering contribution not related to the overall structure. From these data the scattering length density distribution within the dendritic structure can be derived. All results obtained for the fully protonated dendrimer under consideration here agree with the deductions obtained previously for a partially deuterated dendrimer having the same chemical structure.