Two-Dimensional Polyamide Networks with a Broad Pore Size Distribution on the Ag(111) Surface

Abstract

Covalently bonded, two-dimensional polyamide networks were prepared by vacuum deposition polymerization under ultra-high-vacuum conditions on the Ag(111) surface. By a careful choice of the annealing conditions, ordered domains of the corresponding oligomers could be also achieved. The layers were characterized by scanning tunneling microscopy. We used the step-growth polymerization between a trifunctional acid chloride and a bifunctional amine, taking place directly on the surface. The resulting polymer networks are nonuniform and show an open porous structure with a broad distribution of pore sizes. Besides large pores of varying shape, also small, 8- to 12-membered polymer rings with a regular shape are formed. A detailed analysis of the pore size distribution gives insight into the influence of the kinetic preference and the role of conformational flexibility for the formation of disordered covalent networks.