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By Marotti F.

The Langmuir approach is without doubt one of the commonest tools for getting ready twodimensionalmolecular assemblies. during this procedure, an answer of an amphiphilic compound in a low-boiling solvent, frequently immiscible with water, is unfold on a water subphase. After the solvent has evaporated, the amphiphilic molecules shape a monolayer within which their hydrophilic heads engage with the water subphase and the hydrophobic tails are directed clear of it. Compression of the monolayer at the water subphase results in a discount of the world on hand consistent with molecule (A), therefore inflicting a rise in floor strain (!). The ensuing π-A isotherm (surface strain as a functionality of the molecular sector at consistent temperature) offers details at the molecular packing in the monolayer, the orientation of the headgroups, the molecular quarter requirement, and attainable interactions with molecules or ions dissolved within the aqueous subphase. The monolayer shaped on the air-water interface may be transferred onto an effective aid (Langmuir-Blodgett deposition). as a result ease in assembling amphiphiles right into a number of skinny motion pictures with outlined composition, constitution, and thickness, the Langmuir and Langmuir-Blodgett (LB) ideas have allowed the improvement of novel practical fabrics through many scientists.

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Additional resources for Cavitand-, Fullerene-, and Porphyrin Porphyrincontaining Mechanically and Optically Active Monolayers

Example text

It is responsible for the intermolecular distance, the molecular orientation, and the degree of order in the film. g. 14 kcal/mol for octanethiol [10]). The third part is a tail group that constitutes the outer surface of the film. The principal driving force for the formation of these films is a specific interaction between the headgroup and the substrate 1 Malformed or defective subunits are excluded since they don’t have the required set of bonding sites for the self–assembly. 2 The monomeric building blocks self-assemble to give the final aggregate but not intermediate structures.

Upon compression, the bright areas gradually fuse to give a uniform image (picture 2) at the point where the liquid condensed phase appears. –A isotherm. This homogeneous image persists between points 2 and 3 even though the transition from liquid condensed to solid phase occurs at 25 mN m–1. At a surface pressure of ca. 37 mN m–1, image 3 shows bright spots, indicating the formation of small condensation nuclei or germs corresponding to the start of the monolayer collapse. These spots cluster (image 4) and fuse as the surface pressure is further raised, evidencing collapse of the monolayer.

The calibration of the BAM used for the present thesis was accomplished using stearic acid (SA) as an amphiphile. 27 a) with a characteristic change in slope at 20 Å2/molecule and ! = 25 mN m–1, which reflects the transition from the liquid phase to the solid phase. When the linear part of the isotherm, corresponding to the solid-condensed phase, is extrapolated to zero pressure, the area per molecule is determined to 22 Å2, which is consistent with the values reported in literature [83]. –A isotherm.

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Cavitand-, Fullerene-, and Porphyrin Porphyrincontaining Mechanically and Optically Active Monolayers by Marotti F.


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