Langmuir-Blodgett Films of 3-Alkylpyrroles Studied by Scanning Tunneling Microscopy

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By use of the Langmuir-Blodgett (LB) technique mono- and multilayers of monomers and their polymers were built up on conductive solid substrates for studies with scanning tunneling microscopy (STM). Monomers, mixed monomers, and polymer monolayers of 3-alkylpyrroles were transferred onto freshly cleaved molybdenum disulfide (MoS2) and highly oriented pyrolytic graphite (HOPG). High-quality images of the mono- and multilayers could be observed by STM after annealing. Monolayers of monomer were highly ordered showing orientational and positional correlation of alkyl side chains. Mixtures of pyrroles with different side chain lengths showed phase separation. Polymer monolayers showed high positional and orientational order and increased side chain packing density with side chain orientation more orthogonal to the surface. Polymer multilayers showed disorder, revealing connectivity and curvature of polymer chains. From the structures observed on solid substrates (gas-solid interface) conclusions are drawn for the polymerization process and the packing of molecules on the Langmuir trough (at the gas-liquid interface). © 1995, American Chemical Society. All rights reserved.

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