The rotational dynamics of the spin probe cholestane dissolved in a narrow distribution poly(n-butyl acrylate) sample has been investigated via electron spin resonance (ESR) spectroscopy. The measurements were carried out in a wide temperature range: different dynamic regions have been recognized, and the coupling of the probe dynamics to the a and secondary relaxations has been revealed. In particular, the coupling with the structural relaxation is ruled by two fractionary Vogel-Fulcher laws (VF). The crossover from one VF region to the other occurs at the temperature T-C = 1.17T(g), signalling the onset of the cooperativity in the dynamics and confirming a behaviour previously observed in ESR studies carried out on polymeric glass-formers. Furthermore, in this work we discuss the activated regime at the highest temperatures and show that the activation energy does not depend on the length of the polymer main- and side-chains, while its onset temperature linearly depends on the chain length.
|Autori interni:||ANDREOZZI, LAURA|
|Autori:||Andreozzi L; Autiero C; Faetti M; Giordano M; Zulli F|
|Titolo:||Dynamic crossovers and activated regimes in a narrow distribution poly(n-butyl acrylate): an ESR study|
|Anno del prodotto:||2006|
|Digital Object Identifier (DOI):||10.1088/0953-8984/18/28/004|
|Appare nelle tipologie:||1.1 Articolo in rivista|