Organo-lined alumina surface from covalent attachment of alkylphosphonate chains in aqueous solution

Abstract

The reaction of octylphosphonic acid with the surface of alumina nanoparticles has been investigated in order to prepare a close packing of grafted-alkyl chains. This goal was attained through a fitting selection of the experimental conditions in terms of pH, reactant amount, reaction time and temperature. DRX, TEM and 31 P MAS NMR spectroscopy are all consistent with an efficient covalent anchorage of the alkylphosphonate chains without degradation of the support, demonstrated by the morphology and texture preservation during the modification. In addition to the textural analysis, nitrogen adsorption isotherms provide additional pieces of information on the interaction energy between the nitrogen molecule and the surface. These data, combined with those supplied by the empirical test of floatability of powders (methanol number test), as well as the adsorption properties of the differently functionalized alumina samples using other probes, such as hexane and water, as a function of the chain loading, provided converging information about surface coverage and the hydrophilic/hydrophobic properties of the various materials. Different conformations are proposed to take into account the different results obtained from vapor adsorption measurements.

Aqueous or solvent based surface modification: The influence of the combination solvent – organic functional group on the surface characteristics of titanium dioxide grafted with organophosphonic acids

“…For the 3PA modified TiO2 in toluene with increasing concentrations, the surface loading increases and the C value decreases from 54 to 24 (Table 3). Since there are more groups attached to the surface, this likely means that the surface becomes more hydrophobic [14,18]. For the sample made in the solvent mixtures ( Table 2) the C value is stable at around 22 and independent of the amount of water used during the reaction.…”

“…If one agrees that a polar contribution to the total adsorption energy is significantly lowered at -196 °C in comparison with the apolar one (due to dispersive forces), and when it is possible to neglect the confinement effects due to the adsorbent porosity (in our case: P25 is non porous), a downward trend in the C value observed for a series of materials exhibiting similar surface chemistry can be used to monitor increasing hydrophobicity of the surface. Although such an analysis has already been used to demonstrate the increased hydrophobic character of organic layers supported on mineral oxides [14,18], much attention should be paid when trying to go too far into the detailed interpretation of the results obtained. For example, there will be higher probability of multisite attachment of nitrogen molecules to downwardly oriented organic species grafted on the oxide surface, which is at variance with the basic assumption of the BET model.…”

“…It is possible to carry out surface modification with PAs in both aqueous [8,[17][18][19] and organic environment (e.g. toluene [8,20], THF [11,19,21,22], methanol/water mixtures [14,23], butanol [24], ethanol [24], dichloromethane [25]).…”

Interfacial Forces in Dispersion Science and Technology

“…Now let us apply Equation (10a) for the case of a ¼ s, b ¼ l, c ¼ v, that is, for the solid particle at a liquid=vapor interface, by taking into account the Young equation: Equation (10b) was used to derive equations for penetration=infiltration of liquids into porous solids of different morphologies: solids with capillaries of different shapes, [31][32][33] solids made of closely packed equal spheres, [34,35] solids made of cylindrical fibers, [36][37][38] solids with irregular porous structure, [39][40][41][42] being the extension of the Carman equation [43,[44][45][46][47][48][49][50][51][52] ). Now, let us apply Equation (10b) to the classical problem of capillary rise.…”

Simple synthesis of Biphosphonates with Excellent Flameproofing Properties

“…Phosphonates [1][2][3] have been hot research targets owing to their obvious advantages, such as good thermal stability and chemical stability, excellent waterproofing and solvent resistance. And phosphonates [4][5][6] were proposed to have potential for ame retardancy to polymers due to their thermal stability.…”