Evidence for access of molecules the size of acetone or pyridine to the intracrystalline tunnels of nanofibre clay (sepiolite) has indicated formation of a new type of organic-inorganic nanocomposites. However, the introduction of larger molecules has been a recurring problem. It is now agreed that for indigo, the molecules are located on the external surface and at the ends of the fibres, thus blocking access to internal tunnels. We claim, however, that it is possible for indigo molecules to access the internal channels of sepiolite. FTIR and XRD analyses have provided evidence for folding of the sepiolite structure preheated at high temperature (above 350 degrees C). By comparison, we have shown that for indigo/sepiolite mixtures treated in the same conditions, no change in the crystalline structure of the sepiolite is observed, and that blue samples, related to Maya blue, with indigo molecules incorporated deeply enough into sepiolite to prevent folding of the tunnels, can be obtained. NMR, FTIR and thermal analysis confirm the interaction of indigo with the water coordinated to magnesium(II) and located inside the internal and external channels of sepiolite. Two other hypotheses are excluded; we show both that zeolitic water is not blocked in the tunnels by indigo, and that if thermal decomposition products of indigo can be formed, they are in a minority.

Compression of mixed Langmuir monolayers made from combinations of dipalmitoyl phosphatidylethanolamine (DPPE) and the semi-fluorinated alkane C8F17C16H33 (F8H16) results in expulsion of the diblock molecule at high pressure. Depending on the DPPE/F8H16 molar ratio, either a monolayer or a bilayer of F8H16 is formed on top of a DPPE-only monolayer. The structure of the hydrocarbon and fluorocarbon layers that constitute the resulting vertically separated bi-or trilayer was determined using grazing incidence X-ray diffraction. The phenomenon is reversible and represents a novel case of vertical, pressure-induced phase separation.

Having first studied the loss of water in sepiolite via TGA, we then observed through FTIR the evolution of the indigo/sepiolite chemical bonds during the Maya blue formation process. Three stages, corresponding to three different temperature domains, were observed. They explain the peculiar properties of this pigment.

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The surface activity of a series of partially fluorinated amphiphiles with a dimorpholinophosphate polar head, a perfluoroalkyl terminal and a hydrocarbon spacer, C n F 2n1 (CH 2 ) m OP-(O)[N(CH 2 CH 2 ) 2 O] 2 (FnCmDMP, m 1 ± 11, n 4 ± 10), was investigated, and the contributions of the CF 2 and CH 2 groups to the energies of adsorption and micellization of the amphiphiles were determined. In the literature, such data are only available for amphiphiles with either totally fluorinated or totally hydrogenated hydrophobes. We determined the impact of the fluorocarbon segment on the contribution of the hydrocarbon spacer to the adsorption and micellization processes. DG mic and DG ads were evaluated as À 4.2 AE 0.5 and À 4.1 AE 0.6 kJ mol À1 per CF 2 group, consistent with results reported on totally fluorinated surfactants (À 3.3 to À 5.2 kJ mol À1 ). In contrast, the values for DG mic and DG ads per CH 2 group (À 1.0 AE 0.4 and À 1.0 AE 0.6 kJ mol À1 , respectively) were substantially lower than those measured for hydrocarbon analogues of the FnCmDMPs (À 2.4 AE 0.4 and À 2.5 AE 0.5 kJ mol À1 ), which fall in the range observed for standard hydrocarbon amphiphiles (À 2.4 to À 3.05 kJ mol À1 ). These results show that a hydrocarbon chain grafted to a fluori-nated chain does not fully participate in the micellization and adsorption processes, and behaves as if it were shorter by a factor of about three. Thus it is primarily the length of the fluorinated chain that controls micellization and adsorption of such surfactants; the spacer plays only a minor role, and great caution must be exercised when applying the 1 CF 2 % 1.5 CH 2 rule. It is proposed that the hydrocarbon spacer adopts a folded conformation in order to better occupy the void volume which results from the difference in crosssections between fluorocarbon and hydrocarbon chains (ca. 30 vs. 20 2 , respectively).