Octadecylphosphonic acid

Woodward J T, Ulman A and Schwartz D K Self-assembled monolayer growth of octadecylphosphonic acid on mica Langmuir 12 3626-9... 

CdMe2 = dimethylcadmium, ZnEt2 = diethylzinc, TMS = trimethylsilyl, (BDMS)2Te = bis(tert-butyldimethylsilyl) telluride, TDPA = tetradecylphosphonic acid, ODPA = octadecylphosphonic acid, SA = stearic acid, LA = lauric acid, OA = oleic acid, MA = myristic acid, ac = acetate, my = myristate, st = stearate, hdx = hexadecylxanthate, ex = ethylxanthate, dx = decylxanthate, TOPO = trioctylphos-phine oxide, HDA = hexadecylamine, DA = dodecylamine, ODA = octadecylamine, TOP = trioctylphosphine, TBP = tributylphosphine, ODE = 1-octadecene, HH = hexadecyl hexadecanoate,... 

Nie, H.-Y. (2010) Revealing different bonding modes of self-assembled octadecylphosphonic acid monolayers on oxides by time-of-flight secondary ion mass spectrometry sihcon vs. aluminum. Anal. Chem., 82,3371-3376. 

SAMs of allgrlphosphonic acids (butylphosphonic acid, octylphosphonic acid, undecylphosphonic acid and octadecylphosphonic acid) on native niekel oxide allow substrates to be functionalized easily. Monolayer formation has been investigated by diffuse reflectance Fourier transform infrared spectroscopy, non-contact mode atomic force microscopy, contact angle measurements and matrix-assisted laser desorption ionization mass spectrometry. Cyclic voltammetry and electrochemical impedance spectroscopy studies showed that the monolayer increased surface resistance to oxidation. 

Figure 14.16 shows the transients for AlMgl samples modified with biphosphonic or aminophosphonic acid samples modified with octadecylphosphonic acid do not show much difference from the unmodified samples. Especially, the aminophosphonic acids show a significant improvement in the corrosion behavior. Sputter profiles on the matrix and inclusions show that similar films are formed on the A1 matrix but that the aminophosphonic acid forms several-nanometer-thick multilayer films on the inclusions, much thicker films than the biphosphonic acid. In this way, the inclusions are effectively passivated with aminophosphonic acids. Similar observations have more recently been made for the effect of phosphonate modification of A16016 alloy [115]. 

Our approach to a "self-assembling" template layer is outlined in Scheme 2. In the first step, co-hexadecenylbromide (27) is hydrosilylated with trichlorosilane and self-assembled to a silicon oxide surface to form a bromide terminated monolayer. Conversion of the bromide to the phosphonate, by reaction with triethylphosphite, is carried out on the assembled monolayer and followed by acid hydrolysis to the phosphonic acid. All of the conversions performed on the surface are followed by ATR-FTIR and XPS, and go to completion to the extent that can be determined by XPS (22). To form the zirconium phosphonate bilayer, the phosphorylated substrate is immersed into an aqueous solution of ZrOCh to bind Zr + at the phosphonic acid sites. To form the complete bilayer, the zirconated surface is then rinsed with water and placed into a solution of octadecylphosphonic acid in order to self-assemble the capping layer according to Scheme 1. 

Figure 1. ATR-FTIR of the C-H stretch region for the A) Zirconated SA template layer, B) Zirconated LB template layer, C) bilayer formed by SA of octadecylphosphonic acid at A, D) bilayer formed by SA of octadecylphosphonic acid at B, E) bilayer formed by capping the LB template layer with another LB layer of octadecylphosphonic acid. The line at 2918 cwr represents the position of the va(CH2) band in crystalline octadecylphosphonic acid. Since there is no aliphatic CH3 group in the SA template, the peak at 2962 cmr in A results from either unreact ester groups or is a methylene stretch of the CH2 adjacent to the phosphonate.

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