Five silica samples (four precipitated silicas provided by commercial suppliers and one with the MCM-41 structure) have been studied by infrared spectroscopy and by a homemade thermogravimetry-infrared spectrum (TG-IR) setup. The silanol amount, accessibility to water, and different alcohols, and the affinity to water of these various silicas were compared and quantified. TG-IR measurements allowed the precise determination of the integrated molar absorption coefficient of the (nu+delta)OH band, epsilon(nu+delta)OH=(0.16+/-0.01) cm micromol(-1). It is independent of the sample origin and the concentration of silanol groups on silicas. For the precipitated dried samples evacuated at room temperature, the silanol concentration COH varies between 3.6 and 7.0 mmol g(-1). It is 5.3 mmol g(-1) in the case of the MCM-41 sample. Exchange experiments with D2O, followed by back-exchanges with different alcohols (methanol, propan-2-ol, 2-methyl-propan-2-ol, and 3-ethyl-pentan-3-ol) have been followed by infrared spectroscopy. All of the silanols of the MCM-41 sample are accessible to water and alcohol molecules. By contrast, about 20% of the silanols in precipitated samples are not exchanged by D2O (internal silanols). Accessibility decreases with alcohol size; the main effect is relative to methanol. Taking into account the sample specific surface areas and the silanol accessibility to D2O, the surface silanol density of precipitated silicas is close to 8 OH per nm2, at maximum coverage. At variance, the silanol surface density of the MCM silica is much lower, 4 OH per nm2. The TG-IR setup has also been used to determine the amount of water adsorbed on silicas through the intensity of the deltaH2O band. It varies linearly with the concentration of adsorbed water, whatever the silica sample. The integrated molar absorption coefficient of two bands, epsilondeltaH2O=(1.53+/-0.03) cm micromol(-1) and epsilon(nu+delta)H2O=(0.22+/-0.01) cm micromol(-1), have been determined. The number of H2O molecules adsorbed per nm2 has been compared on the five samples under an equilibrium pressure of 13 hPa at room temperature. Taking into account the number of silanols accessible to D2O for each sample, the silica-water affinity has been defined by the H2O/(SiOHsurf) ratio. It is close to 0.8-0.9 for the precipitated samples but lower (0.7) in the case of the MCM one. This result is explained by the more important amount of isolated silanol groups presented by this sample.

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Poly(vinylidene difluoride) (PVDF) films were irradiated by means of heavy ions (in the electronic stopping‐power range) and electrons. Both types of ionizing radiation induce in the polymer film ionizations and excitations, but swift heavy ions induce a huge density of excitations and ionizations along the ion path. Dose‐range goes from 0.3 to 40 MGy. Irradiations were performed with Kr ions in the presence of helium, hydrogen, deuterium, and oxygen. Fourier transform infrared (FTIR) transmission measurements show differences in the nature of the created defects. Triple bonds are characteristic of the Kr ion irradiation. Double bonds, isolated and conjugated, exist for both kinds of radiation, but concentrations are higher with the Kr radiation. The presence of oxygen during irradiation produces oxidization defects. Typical bands of hydroxyls and carbonyls can be seen, respectively, in the 3800‐3000 cm−1 zone and ca. 1850–1730 cm−1. The formation of conjugated double bonds is enhanced when the Kr irradiation is performed under an O2 atmosphere. © 1994 John Wiley & Sons, Inc.

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relevant, (see box in Figure 16), then D would be the lower limit of the thickness, probably near half the true value. SummaryWe presented a series of investigations of some structural aspects of silver metal liquidlike films. Optical and electron microscopy confirmed the colloidal nature of these films and gave insight into the size of the particles and their layout in the film. Different films exhibited very similar structural patterns. Although minor differences abound, no clearcut major differences between MELLFs and black, granular interfacial films, can be stated at this stage.Densitometry and moire deflectometry gave measures of the thicknesses of the film and their silver contents and indicated dynamic distribution of the silver colloid between the MELLF and the organic phase.Acknowledgment. We thank O. Kafri for the moire measurements, S. Shtutina for her invaluable help in the microscopy work, and U. Shmuelli and I. Goldberg for the densitometer and their advice. The partial support of the USA-Israel Binational Foundation to M.D. is gratefully acknowledged.