Order–disorder transition as a function of surface coverage for n-hexadecanoic acid chemisorbed on aluminium

Abstract

Fourier transform infrared multiple specular reflectance (FTIR-MSR) spectroscopy has been applied to study the chemisorption ofn-hexadecanoic or palmitic acid [CH3(CH2)14COOH] on aluminium as a function of surface coverage. The intensity of the symmetric carboxylate stretching vibration has been used to estimate the surface coverage. The intensities and band positions of the CH stretching modes are presented as a function of surface coverage. A sudden transition at about 80% of monolayer coverage is observed for the intensity as well as the position of the CH 2 stretching modes. The intensity changes correspond to a change from a more or less planar orientation of the polymethylene chains at low surface coverage to an almost perpendicular orientation at high surface coverage. The asymmetric CH 3 stretching vibration exhibits a shift opposite to and smaller than what is observed for the CH 2 vibrations. No significant changes are observed for the position of the symmetric CH 3 stretching vibration. However, for the symmetric carboxylate stretching vibration a sudden shift of the band position is observed of the same magnitude, but opposite to the shifts of the CH 2 vibrations.4926

Migration of Additives in Polymer Coatings: Phosphonated Additives and Poly(vinylidene chloride)‐Based Matrix

“…[46][47][48] It may be that the phosphonic acids react with the metal surface native oxide layer [49] by hydrogen bonding [41,50,51] leading to a resonance-stabilized phosphonated complex (tridentate coordination) ( Figure 5), or by proton transfer (possibly reversible), [52] as proposed for carboxylic acids. [53,54] Furthermore, a visual observation of the coating showed a fast coloration. A complexation between phosphonic acids of the additive and the metallic substrate could be the reason for this coloration, and this would account for the improved adhesion of the coating.…”

Adsorption and stability of phthalic acid on a colloidal silver surface: surface-enhanced Raman scattering study

“…Usually, the two oxygen atoms of a carboxylate ion are symmetrically bonded to silver resulting in either a bridging or a bidentate state. 22,27,28 Considering the steric hindrance between the two carboxylate groups in PA 2 , the formation of a unidentate state would not be unrealistic, however. In fact, in a crystalline state of PA the two carboxyl groups are known to be rotated by 33°with respect to the benzene ring moiety.…”

Understanding Organic Film Behavior on Alloy and Metal Oxides

“…The number of hydroxyl groups on the surface of the metal could affect the film formation by behaving as anchoring sites for the acid 14, 16, 35, 38, 64. Conversely, Lu et al observed that for Ti oxide surface, the formation of SAMs was not affected by surface hydroxyls 82.…”

“…The theories rely on a combination of organic and surface parameters such as oxide content of the alloy, organic moiety pKa, basicity of the surface,14 and hydroxyl content 14, 16, 35, 38, 64. In the two alloys studied here, the surfaces are composed of the oxides of the metals in similar ratios to the bulk alloy 4, 32, 37, 50, 65.…”