Comparison of Calorimetric and Dielectric Single Component Glass Transitions in PtBS−PI Blends

Microscopic versus Macroscopic Glass Transition(s) in Blends of Industrial Interest

We investigate by neutron scattering and calorimetry a mixture of styrene-butadiene rubber (SBR) and a commercial resin. The neat materials present a large dynamic contrast, having SBR a much lower glass-transition temperature than the resin. The focus is to exploit neutron scattering selectivity in an isotopically labelled sample where deuterated SBR is the majority component. This direct insight into the resin atomic motions within the mixture allows determining the ‘microscopic’ glass transition of the resin in the presence of the a priori much more mobile SBR. This transition takes place in the vicinity of the initial calorimetric glass transition temperature, mainly dictated by the majority component.

Dielectric relaxation of polymers: segmental dynamics under structural constraints

In this article we review the recent polymer literature where dielectric spectroscopy has been used to investigate the segmental dynamics of polymers under the constraints produced by self-structuring. Specifically, we consider three cases: (i) semicrystalline polymers, (ii) segregated block-copolymers, and (iii) asymmetric miscible polymer blends. In these three situations the characteristics of the dielectric relaxation associated with the polymer segmental dynamics are markedly affected by the constraints imposed by the corresponding structural features. After reviewing in detail each of the polymer systems, the most common aspects are discussed in the context of the use of dielectric relaxation as a sensitive tool for analyzing structural features in nanostructured polymer systems.