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RELAXATION PHENOMENA IN MIXED ISOMERIC ALCOHOLS BY MANDELSTAM-BRILLOUIN SCATTERING (Articolo in rivista)

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RELAXATION PHENOMENA IN MIXED ISOMERIC ALCOHOLS BY MANDELSTAM-BRILLOUIN SCATTERING (Articolo in rivista) (literal)

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Alternative label

MAJOLINO, D and MIGLIARDO, P and ALIOTTA, F and MAGAZU, S and VASI, C and DAPRANO, A and DONATO, DI and LIVERI, VT (1991)
RELAXATION PHENOMENA IN MIXED ISOMERIC ALCOHOLS BY MANDELSTAM-BRILLOUIN SCATTERING
in Molecular physics (Print); TAYLOR & FRANCIS LTD, London (Regno Unito)
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

MAJOLINO, D and MIGLIARDO, P and ALIOTTA, F and MAGAZU, S and VASI, C and DAPRANO, A and DONATO, DI and LIVERI, VT (literal)

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MAJOLINO, D (Reprint Author), UNIV MESSINA,DIPARTIMENTO FIS,CONTRADA PAPARDO,POB 55,I-98166 S AGATA,ITALY. CNR,IST TECN SPETTROSCOPICHE,I-98166 S AGATA,ITALY. UNIV PALERMO,IST CHIM FIS,I-98123 PALERMO,ITALY. CNR,CISM,GRP NAZL STRUTTURA MAT,I-98166 S AGATA,ITALY. (literal)

Titolo

RELAXATION PHENOMENA IN MIXED ISOMERIC ALCOHOLS BY MANDELSTAM-BRILLOUIN SCATTERING (literal)

Abstract

Mandelstam-Brillouin scattering data in mixed isomeric alcohols n-pentanol (nPe-OH) and 2-methyl-2-butanol (2Me-2BuOH) are presented. The hypersonic velocity and normalized absorption are measured as a function of the scattering angle, in the temperature range from - 15-degrees-C to + 45-degrees-C, and as a function of n-PeOH molar fraction going from the pure n-PeOH to the pure 2Me-2BuOH. The experimental results confirm the existence of a shear relaxation phenomenon in the GHz region, that has been previously detected in pure liquids. The temperature dependence of the relaxation time tau-s and of the shear modulus G-infinity evaluated within viscoelastic liquid models, support the existence of open heterostructures in the 2-methyl-2-butanol rich phase. A detailed analysis is also carried out for the measured shear viscosity eta-s, whose temperature dependence becomes more and more non-Arrhenian by adding normal pentanol (n-PeOH) to its stereoisomer (2Me-2BuOH). A comparison between the shear flow mean activation enthalpy and the high frequency shear relaxation enthalpy allows us to demonstrate the more `fragile' behaviour of 2Me-2BuOH and of its more concentrated mixtures with respect to that of n-PeOH, confirming that the observed non-ideal behaviour in the mixing process can be associated with the existence of H-bond imposed structural aggregates that are in dynamic equilibrium. (literal)

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