Surface carboxylic acid groups

In a concurrently published report [160] Crooks and coworkers reported similar MUA-SAMs modified by covalent linking of hyperbranched macromolecules. These films containing a high density of surface carboxylic acid groups could selectively bind metal ions or undergo chemical modification. 

A unique dendrimer series possessing an all-hydrocarbon interior and up to 36 surface carboxylic acid groups has exhibited very interesting unimolecular micelle properties. These products have been shown to form host-guest complexes with various hydrophobic guest molecules. Newkome refers to these products as micellanes [137, 138]. 

The behaviour of the latex particles containing significant amounts of surface carboxylic acid groups was pathologically abnormal. The UCFT in these systems increased with increasing amounts of surfactant until a maximum value was reached. Thereupon its value declined, asymptoting to that of the 0L-temperature. The value of the UCFT at the maximum exceeded the 0L-temperature by as much as 20 °C at this pH, well beyond the limits of experimental error ( 2 °C). 

Finally, we note that the maximum in the UCFT observed with poly(vinyl alcohol) is readily explicable without the elastic repulsion hypothesis. It merely requires the adsorbed, partially hydrolysed polymer to change from a relatively flat conformation at lower concentrations to a conformation more extended normal to the interface, and thus exhibiting reduced multipoint anchoring, at higher concentrations. This explanation is closely analogous to that proposed by Dobbie et al. (1973) for poly(oxyethylene) attached to polystyrene latices containing surface carboxylic acid groups. 

Figure 10.1 Schemes showing (a) ND-Oleylamine (ND-OLA) complex produced from interactions between oleylamine and a surface carboxylic acid group of NDs, and (b) the arrangement of oleylamine on the particle surface that can stabilize the ND in organic solvents. Reprinted from [52] Copyright 2010, with permission from Elsevier.

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