Polymers under 2-D Confinement: Flow of Polymer Melts at the Nanoscale

Abstract

With the recently developed nanofluidic method one is able to follow in situ the imbibition of polymers into nanotubes. Therefore, pieces of nanoporous anodic aluminum oxide (AAO) are coated with gold electrodes on the top and bottom face. The dielectric response is recorded while the polymer imbibes into the cylindrical nanopores of ≈ 100 μm length and 12-200 nm radius. The method provides simultaneous access to the imbibition kinetics and the associated polymer dynamics (at the segmental and chain length scales) during polymer flow. Two models- a parallel and a series model- with different interactions between the polymer/AAO are investigated with respect to the evolution of the dielectric strength and of the characteristic relaxation times. The model predictions are compared and tested against existing results from two polymers: a polar polymer (poly(n-butyl methacrylate), PnBMA) and a non-polar polymer (cis-1,4-polyisoprene, PI). In the case of PI, where the longest normal mode was probed, it was shown that the dielectric strength during imbibition deviates from the usual dependence. The results are discussed in terms of increasing adsorption sites with time. We further discuss the potential of the method in current polymer physics problems of interest. © 2021 American Chemical Society. All rights reserved.