Size-effects on the segmental dynamics of sub 10-nm segregated polydimethysiloxane

Resumen del trabajo presentado a la 10th Conference on Broadband Dielectric Spectroscopy and its Applications (BDS) celebrada en Bruselas (Belgica) del 26 al 31 de agosto de 2018.Confining glass-forming polymer melts has been a way to look for the size effects on the segmental scale dynamics, which would be expected to occur on cooling down the liquid towards the glass transition, in connection with the corresponding growing size of the cooperatively rearranging regions. As far the growing size becomes comparable to the confinement distances, a change in the temperature dependence of the segmental mobility time has been anticipated. Despite of this expectation, reported experimental results obtianed so far are rather contradictory. A reason for the discrepancies is the important role of interfaces, which in many cases largely affects the segmental dynamics. Unraveling the genuine size effects from those attributable to the presence of interfaces can be extermelly difficult. In this work we show how the segmental dynamics of poly(dimethylsiloxane), PDMS, is modified in systems pressenting PDMS segregated phases of varying geometry and sizes. Most of the considered systems present obvious changes in the dynamics that can be mainly attributed to the presence of interfaces. However, there is a single case where effects directly connected with the growing size of the cooperatively rearranging regions are found. In this particular case, a segregated PDMS phase with sub-10 nm size in the three dimensions is present. Contrarly, segregated sub-10 nm lamellar PDMS phases do not manifest such a behavior, the single effect in the later case being the general slowing-down of the segmental dynamics induced by the presence of rigid interfaces.Peer reviewe