Blodgett Monolayers

The G5 and G6 dendrons did not assemble into monolayers because of the tendency of the focal point to be encapsulated by the hydrophobic dendritic branches at higher generations. Similarly, Liskamp s group reported a series of amino acid based dendrons capped with Boc end groups and a focal fatty acid chain also formed stable monolayers however, the fatty acid group was not a significant improvement over a shorter linkage (Mulders et al. 1998). In the condensed mono-layer phase, the dendrons covered a smaller area than predicted for a fully spread 

No stabie Monoiayers obsen/ed for more sphericai G5 and G6 dendrons 

STRUCTURE AND SELF-ASSEMBLY OF AMPHIPHILIC DENDRIMERS IN WATER 

When a more globular conformation is enforced by functionaUzing the PPI dendrimers with bulky adamantyl terminal groups, or at higher generations (G4 and G5) of the PAMAM system, the dendrimers behave like nonamphiphUic, hydro-phobic spheroids. 

X-ray reflectivity studies and II-A isotherms revealed a similar model in which the dendrons project the hydrophUic crowns into the water phase and the hydrophobic chains perpendicular to the interface. Amphiphihc dendronized polymers that adopt a cylindrical, rodlike morphology, projecting hydrophihc and hydrophobic dendrons on opposite faces of the stmcture, form stable monolayers exhibiting collapse pressures of approximately 20mN/m (Fig. 11.41). 

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Outka D A, Stdhr J, Rabe J P, Swalen J D and Rothermund FI FI 1987 Orientation of araohidate ohains in Langmuir-Blodgett monolayers on Si(111) Phys. Rev. Lett. 59 1321-4... 

MI] Tredgold R H and Winter C S 1981 Tunneling currents in Langmuir-Blodgett monolayers of stearic acid J. Phys. D Appl Phys. 14 LI 85-8... 

Peterson I R 1986 A structural study of the conducting defects in fatty acid Langmuir-Blodgett monolayers J. Mol. Electron. 2 95-9... 

Kim K S, M A Moller, D J Tildesley and N Quirke 1994a. Molecular Dynamics Simulations Langmuir-Blodgett Monolayers with Explicit Head-group Interactions. Molecular Simidati 13 77-99. 

Recent developments in Raman equipment has led to a considerable increase in sensitivity. This has enabled the monitoring of reactions of organic monolayers on glassy carbon [4.292] and diamond surfaces and analysis of the structure of Lang-muir-Blodgett monolayers without any enhancement effects. Although this unenhanced surface-Raman spectroscopy is expected to be applicable to a variety of technically or scientifically important surfaces and interfaces, it nevertheless requires careful optimization of the apparatus, data treatment, and sample preparation. 

Magnetic field effects on photoelectrochemical responses of modified electrodes with Langmuir-Blodgett monolayer containing porphyrin-viologen linked compounds. Mol. Cryst. Liq. Cryst., 294, 221-224. 

The first process is due to Schottky barriers [30], which are electrical dipole moments that form at the metal I molecule interfaces, as discussed above [34,40]. The second process arises if the electrically-active portion of the molecule is placed asymmetrically within the metal I molecule I metal sandwich. This geometry is common, because a long alkyl tail is often needed to make the molecule amphiphilic so that it will form well-ordered Langmuir-Blodgett monolayers [76-78]. 

Geddes NJ, Sambles JR, Jarvis DJ, Parker WG, Sandman DJ (1990) Fabrication and investigation of asymmetric current-voltage characteristics of a metal/Langmuir-Blodgett monolayer/metal structure. Appl Phys Lett 56 1916-1918... 

Baldwin JW, Amaresh RR, Peterson IR, Shumate WJ, Cava MP, Amiri MA, Hamilton R, Ashwell GJ, Metzger RM (2002) Rectification and nonlinear optical properties of a Langmuir-Blodgett monolayer of a pyridinium dye. J Phys Chem B106 12158-12164... 

Tredgold RH, Winter CS (1981) Tunnelling currents in Langmuir-Blodgett monolayers of stearic acid. J Phys D Appl Phys 14 L185... 

This approach may also be applied to racemic bilayers built up from homo-chiral Langmuir-Blodgett monolayers. By measuring the two-dimensional diffraction pattern from such a bilayer it is possible to deduce the molecular chirality of each of the two monolayers in the order they were inserted to construct the bilayer. This approach can be extended to multilayers. Thus, in principle, we close the circle started in Section IV-G-1. It is possible to assign the absolute configuration of chiral molecules in centrosymmetric crystals provided that one can construct the crystal (in this case the multilayer) by adding homochiral layers one by one. 

Peleshanko S, Sidorenko A, Larson K, Villavicencio O, Omatska M, McGrath DV, Tsuknik VV. Langmuir-Blodgett monolayers from lower generation amphiphilic monodendrons. Thin Sohd Films 2002 406 233-240. 

Xie R, Bryant GW, Zhao J et al (2003) Tailorable acceptor Cgo-nBn and donor Cgo-niNm pairs for molecular electronics. Phys Rev Lett 90 206602/1-206602/4 Metzger RM (2003) One-molecule-thick devices rectification of electrical current by three Langmuir-Blodgett monolayers. Synth Met 137 1499-1501... 

Metzger RM, Baldwin JW, Shumate WJ et al (2003) Electrical rectification in a Langmuir-Blodgett monolayer of dimethyanilinoazafullerene sandwiched between gold electrodes. J Phys Chem B 107 1021-1027... 

Fig. 6 (a) Scanning electron and (b) atomic force microscopy images of copper phthalocyanine Langmuir-Blodgett monolayer FETs. (c) Hole field-effect mobility as a function of the copper phthalocyanine channel length... 

FIGURE 3.9. I(V) characteristics at 295 K and 77 K for Langmuir-Blodgett monolayer of fatty acid (CH3(CH2)nCOOH) on Al. Junction area is 0.2 cm2. Reprinted with permission from Ref.69 Polymeropoulos et al., J. Chem. Phys. 69, 1836-1847 (1978). Copyright 1978 American Institute of Physics. 

Langmuir-Blodgett Monolayers in Molecular Electronic Devices... 

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