Fatty acid modified dendrimers in bulk and solution: Single-chain neutron scattering from dendrimer core and fatty acid shell

Small-angle neutron scattering (SANS) has been applied to extract the singl e-chain form factors of the fatty acid (FA) and the dendrimer components in bulk and dilute solution of fatty acid modified poly(propyleneimine) dendr imers (Astramol). The fatty acid chains were covalently or noncovalently li nked to the end groups of two generations, G3 and G5. Bulk samples were pre pared under contrast match conditions of mixtures of dendrimer-h/FAH and de ndrimer-h/FAD to obtain the form factor of the fatty acid components. The s olutions were prepared with deuterated fatty acid modified dendrimers in de calin solvent using the contrast match technique. Mixtures of decalin-h and decalin-cl were used to match either the dendrimer or FA components. The d endrimer core of both G3 and G5 appears collapsed, without the incorporatio n of a significant amount of solvent. The G3 FA portion has a size closer t o that of the bulk than that of a collapsed FA shell. The G5 dendrimer has the opposite trend.