SELF-ASSEMBLED MULTILAYER FILMS FROM DENDRIMERS

Composite molecular films of(AB), type are fabricated by self-assembly of dendritic macromolecules of two adjacent generations using the ele ctrostatic layer-by-layer deposition. Polyamidoamine dendrimers with s urface amine groups for generations 4, 6, and 10 (G4, G6, G10) and car boxylic groups for generations G3.5, G5.5, and G9.5 have been used as building units. The molecular films are explored by scanning probe mic roscopy and X-ray reflectivity. All even generations are observed to f orm homogeneous, stable monolayers on a silicon surface. The thickness of a single monolayer varies with generation (molecular weight) from 1.8 nm (G4) to 2.8 nm (G6) and 5.6 nm (G10). Average thickness of a mo lecular layer in multilayer films is much smaller than the diameter of ideal spherical dendritic macromolecules. The model of molecular orde ring of dendrimer films assumes compressed dendritic macromolecules of oblate shape with the axial ratio in the range from 1:3 to 1:6. The h igh interaction strength between ''sticky'' surface groups along with short range van der Waals forces and long range capillary forces are c onsidered to be responsible for formation of compact monolayer structu res. A tendency to higher spreading of high generation dendrimers obse rved here corresponds to the surface behavior predicted by molecular d ynamic simulations.