The combination of neutron spin echo and dielectric spectroscopy to examine tube dilation

¹ Materials Physics Center (MPC), Centro de Física de Materiales (CFM) (CSIC-UPV/EHU), Paseo Manuel de Lardizabal 5, 20018 San Sebastián, Spain
² IKERBASQUE-Basque Foundation for Science, Euskadi Plaza 5, 48009 Bilbao, Spain
³ Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología, University of the Basque Country (UPV/EHU) PO Box 1072, 20018 Donostia, Spain
⁴ Jülich Centre for Neutron Science, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
⁵ Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20156, Cedex 9 38042 Grenoble, France
⁶ Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 Donostia, Spain

^* Corresponding author: juan.colmenero@ehu.eus

Published online: 17 November 2022

Abstract

The polymer dynamics in blends of long and short chains spans several decades in time and the understanding of the effect of the short chains on the relaxation mechanism of the long chains due to constraint release requires the combination of microscopic and macroscopic techniques. While the longtime dynamics can be accessed by mechanical or dielectric spectroscopy (DS), its relation to the microstructural details requires the application of theoretical models. In contrast, neutron spin echo (NSE) measures directly the dynamic structure factor reflecting the process of constraint removal at the molecular scale. Here the comparison of NSE and DS results in a model blend of short and long polyisoprene enables the exploration of the entire time regime showing that constraint release leads to a dilation of the confining tube. We show the description of the dynamic tube dilation using a simple model in which the time controlling the tube dilation for the long chain is the terminal time of the short chain.