Long-range ordered monolayer domains of the polymer poly(p-phenylene-terephthalamide) were directly synthesized on the Ag(111) surface and analyzed by scanning tunneling microscopy with submolecular resolution. The polymerization reaction of the monomers runs at room temperature and yields ordered domains with a diameter of up to 50 nm. The lateral order of the polymer chains within these domains is similar to that known for bulk crystals but reveals deviations that are caused by the role of the underlying Ag(111) surface. The polymer shows a chain folding to re-enter the ordered domains, which is in accordance with known models of crystalline bulk polymers.
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.
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