Structure of Langmuir-Blodgett Films of Disk-Shaped Molecules Determined by Atomic Force Microscopy

Abstract

Monolayer Langmuir-Blodgett films of a discotic mesogen have been studied with atomic force microscopy (AFM). These measurements confirm the "edge on" arrangement for the disk-shaped molecules suggested by surface pressure-area isotherms and show that the molecules form columns that are separated by 17.7 angstroms +/- 10 percent. Column alignment is found to be predominantly along the film deposition direction, with an angular spread of 35 degrees . The AFM images also show that the mean disk separation within the columns is 5.1 +/- 1.3 angstroms, in good agreement with x-ray diffraction (XRD) results. Roomtemperature XRD measurements on bulk samples of the same material indicate a disordered-hexagonal liquid crystalline mesophase, with a column-to-column spacing of 19.9 +/- 0.2 angstroms.

Structural Studies of Langmuir Films of Disc-Shaped Molecules

“…After transfer of these triphenylene films to solid substrates, atomic force microscopy and GIXRD clearly indicated columnar structures. [14,17,18] XRR and GIXRD studies of 3a and 3b at the air±water interface unambiguously established monolayer edge-on columnar structure, albeit with a 10±30 % occupied second layer. [19] Furthermore, a detailed analysis of the XRR profiles (Fig.…”

A Structural Study of Amphiphilic PAMAM (Poly(amido amine)) Dendrimers in Langmuir and Langmuir–Blodgett Films

“…So the column-like structure at microscale characterizes the edge-on arrangement. For the Langmuir films at the air/water interface, the disk-shaped amphiphilic dendrimers with strong core-core interaction and relatively weak core-water interac-tion will show the edge-on arrangement; otherwise, they will show the face-on arrangement (15,16). By the surface chemistry studies of HA-PAMAM dendrimer (generation IV) (17) and pentacosadiynoic acid modified PAMAM (PDA-PAMAM) dendrimer (18), our research group shows that besides the corecore and core-water interaction, the functional end groups of the dendrimers can also affect the dendrimer molecule arrangement in Langmuir films.…”

Cross-Section Molecular Imaging of Supramolecular Microtubes with Contact Atomic Force Microscopy

“…[1] To gain better insight into the mechanism of the Diels ± Alder reaction, we reconstructed the whole butadiene ± ethylene reaction pathway by means of the intrinsic reaction coordinate (IRC) approach. [2] Then, selected structures were extracted to obtain their orbitals, geometries, and energies. We were surprised to witness that the various orbital interactions do not occur simultaneously during the Diels ± Alder reaction.…”

“…[1,2] In particular, AFM has been used to study two-dimensional, ordered organic molecules adsorbed on well-defined surfaces and at interfaces. [3] While there is an increasing number of studies on AFM imaging of biological macromolecules, [4±6] only a few reports [7±10] have described the morphologies and molecular orientation for synthetic supramolecular assemblies.…”