Search

A detailed vibrational and permettivity study, performed on associated liquids (alcohols) “dispersed” in $CCl_4$, is presented. The experimentally obtained data, taken at a concentration limit as low as $l0^-^3M$ allow to explain the growth mechanism present in such systems (normal-pentanol and 2-methyl-2-butanol), starting from the monomeric state up to oligomers, by increasing the concentration values. Furthermore the behavior of the measured Kirkwood correlation factor $g_k$ indicates that the cychc speeies ($g_k < 1$) are the first existing aggregates, independently from the systems. The interaction among the monomers induces anharmonic effects into the original $o-H$ stretching, lowering the center frequencies and enlarging the linewidths. When the concentration increases the more hindered alcohol (2M-2BuOH) reveals mainly the existence of cyclic dimers ($g_k$ < 1), whereas a growth process of linear $n$-mers is evidenciated for the linear normal-pentanol width a simultaneous disappearance of the cyclic structures.

Non destructive analysis, by means Raman and FTIR spectroscopy, of constituents of the pigments and bulk ceramics of neolithic Sicilian samples is presented. Both the spectroscopies applied in “situ”, on bulk and pigments, allows us to identify the elemental constituents of the samples as well as their chemical composition and symmetry.

An analysis of Rayleigh wing spectra on two isomers of propanol ($C_3H_7OH$) and on two its Br-based isomorphous ($C_3H_7Br$), is presented. The performed measurements, over a wide temperature range, allow us to identify two different processes characterizing the response of both the alcohols. A comparison between the rotational dynamics of the linear normal-propanol (1-Propanol) and the more sterically hindered iso-propanol (2-Propanol) is performed. At the same time, the role played by the H-hond in the associative properties of hydrogenous systems is investigated by comparing the dynamical response of the two alcohols with that of 1-Br propane and 2-Br propane, in which the O-H “active” sites are replaced by “inert” bromine atoms.

In the present study the results of an extensive experimental investigation, perfomed as a function of concentration and temperature, by means of density, viscosity, refraction index and ultrasonic velocity measurements on aqueous solutions of Poly (ethylene Glycol) (PEG) of Molecular Weight (M.J.) 400 and 600, are reported. The experimental data show, in short, that the water added to the pure polymer bonds itseif, by H-bond, to the oxigens of the oxirane groups, each oxigen being able to bond up to two water molecules in the first hydration shell.

Non destructive analysis, by means Raman and FTIR spectroscopy, of constituents of the pigments and bulk ceramics of neolithic Sicilian samples is presented. Both the spectroscopies applied in “situ”, on bulk and pigments, allows us to identify the elemental constituents of the samples as well as their chemical composition and symmetry.

A detailed vibrational and permettivity study, performed on associated liquids (alcohols) “dispersed” in $CCl_4$, is presented. The experimentally obtained data, taken at a concentration limit as low as $l0^-^3M$ allow to explain the growth mechanism present in such systems (normal-pentanol and 2-methyl-2-butanol), starting from the monomeric state up to oligomers, by increasing the concentration values. Furthermore the behavior of the measured Kirkwood correlation factor $g_k$ indicates that the cychc speeies ($g_k < 1$) are the first existing aggregates, independently from the systems. The interaction among the monomers induces anharmonic effects into the original $o-H$ stretching, lowering the center frequencies and enlarging the linewidths. When the concentration increases the more hindered alcohol (2M-2BuOH) reveals mainly the existence of cyclic dimers ($g_k$ < 1), whereas a growth process of linear $n$-mers is evidenciated for the linear normal-pentanol width a simultaneous disappearance of the cyclic structures.

In the present study the results of an extensive experimental investigation, perfomed as a function of concentration and temperature, by means of density, viscosity, refraction index and ultrasonic velocity measurements on aqueous solutions of Poly (ethylene Glycol) (PEG) of Molecular Weight (M.J.) 400 and 600, are reported. The experimental data show, in short, that the water added to the pure polymer bonds itseif, by H-bond, to the oxigens of the oxirane groups, each oxigen being able to bond up to two water molecules in the first hydration shell.

An analysis of Rayleigh wing spectra on two isomers of propanol ($C_3H_7OH$) and on two its Br-based isomorphous ($C_3H_7Br$), is presented. The performed measurements, over a wide temperature range, allow us to identify two different processes characterizing the response of both the alcohols. A comparison between the rotational dynamics of the linear normal-propanol (1-Propanol) and the more sterically hindered iso-propanol (2-Propanol) is performed. At the same time, the role played by the H-hond in the associative properties of hydrogenous systems is investigated by comparing the dynamical response of the two alcohols with that of 1-Br propane and 2-Br propane, in which the O-H “active” sites are replaced by “inert” bromine atoms.