Polymer Nanofluidics by Broadband Dielectric Spectroscopy

Abstract

A multitude of experimental techniques can be employed to investigate the dynamics of polymers under condition of geometric confinement. Among them, Broadband Dielectric Spectroscopy has proven its strength in this research field, being used in numerous investigations on polymer dynamics in samples having one, two, or three dimensions on the nanometer length scale. However, in most cases, the investigated polymers were subjected to constraints arising only from a “static” confinement, where the dimensionality of the confining geometry and the interfacial interactions played the most important role. In addition to these static factors, kinetic constraints and frustrations arise when polymers are flowing in nanometric confinement. Measuring polymer dynamics during flow in nanoconfinement is a challenging task, which requires the development of new experimental procedures and methods. Here, we show that different aspects of the flow process of polymers in cylindrical nanopores can be investigated by means of Broadband Dielectric Spectroscopy, using a recently developed experimental approach, which employs highly ordered nanoporous media as nanofluidics cell. No significant shifts in the glassy dynamics of poly-2-vinylpyridine (P2VP) investigated during capillary flow into nanopores are found down to a pore diameter of 18 nm. In the case of phase-separated polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP) flowing into nanopores, no shifts in the dynamic glass transition of the P4VP blocks are observed down to a confinement size allowing the flow of only one (single) copolymer domain.