SEMIPERMEABLE, CHEMISORBED ADLAYERS OF FOCALLY-SUBSTITUTED ORGANOTHIOL DENDRONS ON GOLD

A series of focally substituted organothiol dendrons of the first thro ugh third generation were used to construct adlayers on a gold surface . The presence and structural features of these adlayers were confirme d by X-ray photoelectron spectroscopy, infrared spectroscopy, and elli psometry. The relative coverage and/or permeability of these adlayers was studied using capacitance and electrochemical blocking experiments . It was found that as the number of hyperbranches in the dendron incr eased from one to three, the dendron adlayers became initially less an d then more permeable. This result indicated a tradeoff between size a nd packing efficiency when using these molecules to cover a surface. T hese data also suggest that the dendrons have formed homogeneous but p ermeable adlayers on the gold surface rather than adlayers consisting of islands of material. These adlayers showed large differences in the ir ability to trap and hold a small molecule, trans-cyclohexanediol, w ithin them.