Effect of Solvent Quality on the Molecular Dimensions of PAMAM Dendrimers

The average dimensions of poly(amido amine) (PAMAM) dendrimers of generations G5 and G8 are studied by small-angle neutron scattering (SANS) as a function of solvents of differing quality, the composition of mixtures of a good solvent and a nonsolvent, and temperature. The radius of gyration, R g, of the G8 dendrimer decreases for the series of solvents D(CD 2 ) m OD (with m = 0, 1, 2, 4) by approximately 10% from m = 0 to m = 4 with decreasing solvent quality. The average segment density in solution is calculated for G5 and G8. The size of PAMAM dendrimers, as reflected by R g, is not influenced by the composition of mixtures of methyl alcohol/acetone in the full range of solubility of the dendrimers. In the temperature range −10 °C ≤ T ≤ 50 °C, the dimensions of the G8 and G5 dendrimer are constant, within ≈5% of each other.