Probing the cooperative and local modes of a poly(methyl acrylate) sample via ESR spectroscopy

Electron spin resonance spectroscopy has been employed to analyze the probe rotational dynamics in a narrow distribution poly(methyl acrylate) melt. Dynamic regions have been found in the investigated temperature range and the coupling of the probe dynamics to the main and secondary polymer relaxations has been studied. The temperature dependence of the shear viscosity has been also measured, and, in the supercooled state of the host, it has been used to reveal the effects on the probe dynamics of both the local stiffness of the polymer and the occurrence of cooperativtity and dynamic heterogeneities in the matrix. Below T, the rotational dynamics follows activated regimes. (c) 2006 Elsevier B.V. All rights reserved.