The dynamics of cholestane spin probes disolved in poly(ethyl acrylate) (PEA) matrics was fully investigated over a wide temperature range by means of ESR spectroscopy. A PEA sample with narrow molecular weight dispersion (PEA1) and a second one (PEA2) doped with about 2.7 wt.-% free ethyl acrylate were employed. Depending on temperature, different dynamical regimes were identified. The coupling between the spin probe dynamics and structural, beta, and gamma relaxation processes was recognised. At higher temperatures, Vogel-Fulcher laws well described the temperature dependence of the spin probe rotation, which tracks the backbone dynamics with different coupling degrees. The experiments provide the chance of evaluating the onset of cooperativity in the different PEA matrics. The information is obtained by comparing the temperature dependence of probe rotation with that of rheolgical measurements. Moreover, the dynamics of cholestane in PEA2 shows an Arrhenius regime in the highest temperature region, which exhibits a complete decouplling form the backbone dynamics.
Rotational Dynamics ESR Investigation of the Cholestane Spin Probe Dissolved in a Narrow Dispersity Poly(ethyl acrylate): Effect of the Presence of Trace Amounts of Free Monomer
ANDREOZZI, LAURA;FAETTI, MASSIMO;GIORDANO, MARCO;CASTELVETRO, VALTER;
2002-01-01
Abstract
The dynamics of cholestane spin probes disolved in poly(ethyl acrylate) (PEA) matrics was fully investigated over a wide temperature range by means of ESR spectroscopy. A PEA sample with narrow molecular weight dispersion (PEA1) and a second one (PEA2) doped with about 2.7 wt.-% free ethyl acrylate were employed. Depending on temperature, different dynamical regimes were identified. The coupling between the spin probe dynamics and structural, beta, and gamma relaxation processes was recognised. At higher temperatures, Vogel-Fulcher laws well described the temperature dependence of the spin probe rotation, which tracks the backbone dynamics with different coupling degrees. The experiments provide the chance of evaluating the onset of cooperativity in the different PEA matrics. The information is obtained by comparing the temperature dependence of probe rotation with that of rheolgical measurements. Moreover, the dynamics of cholestane in PEA2 shows an Arrhenius regime in the highest temperature region, which exhibits a complete decouplling form the backbone dynamics.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
