Interfacial Interactions During In Situ Polymer Imbibition in Nanopores

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Interfacial Interactions During In Situ Polymer Imbibition in Nanopores

Chien-Hua Tu, Jiajia Zhou, Masao Doi, Hans-Juergen Butt, and George Floudas

Phys. Rev. Lett. 125, 127802 – Published 17 September 2020

Abstract

Using in situ nanodielectric spectroscopy we demonstrate that the imbibition kinetics of cis-1,4-polyisoprene in native alumina nanopores proceeds in two time regimes both with higher effective viscosity than bulk. This finding is discussed by a microscopic picture that considers the competition from an increasing number of chains entering the pores and a decreasing number of fluctuating chain ends. The latter is a direct manifestation of increasing adsorption sites during flow. At the same time, the longest normal mode is somewhat longer than in bulk. This could reflect an increasing density of topological constraints of chains entering the pores with the longer loops formed by other chains.

Received 15 July 2020
Accepted 21 August 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.127802

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Capillary interactions Confinement Interface & surface thermodynamics Polymer behavior Polymer conformation & topology

Porous media

Polymers & Soft Matter

Authors & Affiliations

Chien-Hua Tu ¹, Jiajia Zhou ^2,3, Masao Doi ³, Hans-Juergen Butt¹, and George Floudas ^1,4,5,*

¹Max Planck Institute for Polymer Research, 55128 Mainz, Germany
²School of Chemistry, Beihang University, Key Lab Bioinspired Smart Interfacial Science & Technology of Ministry of Education, Beijing 100191, China
³Center of Soft Matter Physics and Its Applications, Beihang University, Beijing 100191, China
⁴Department of Physics, University of Ioannina, 45110 Ioannina, Greece
⁵University Research Center of Ioannina (URCI)—Institute of Materials Science and Computing, 45110 Ioannina, Greece

^*Corresponding author. gfloudas@uoi.gr

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Issue

Vol. 125, Iss. 12 — 18 September 2020

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Images

Figure 1
Schematic of the AAO-sample geometry for the in situ imbibition of cis-1,4-polyisoprene. In the upper part the dipole moment components along ( $μ_{|}$ ) and perpendicular ( $μ_{⊥}$ ) to the chain contours are indicated. The direction of the $E$ field with respect to the end-to-end vector (thick arrow) is shown in the right. The electric filed is applied in the $z$ direction (flow direction), hence the $z$ component of the polarization is detected.
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Figure 2
(a) Dielectric loss curves of bulk and confined PI-42k within AAO pores with pore diameters of 100, 40, and 20 nm at $T = 303 K$ . The black dashed line indicates the peak position of the longest normal mode in bulk PI. Representative fit of the dielectric loss curve for the bulk PI-42k with a summation of two HN functions corresponding to the longest normal mode (blue shaded area) and the summation of shorter normal modes (red shaded area). (b) Evolution of the relaxation times for PI-42k during imbibition inside AAO nanopores as a function of the square-root of time. Same color codes as in (a): 100 (orange circles), 40 (green squares), and 20 nm (blue rhombi). The short dashed lines give the position of the longest normal mode and of the internal modes in the bulk polymer at the same imbibition temperature.
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Figure 3
(a) Evolution of the dielectric loss spectra of PI 42k during imbibition within AAO nanopores with pore diameter of 40 nm at 303 K. (b) The extracted dielectric intensity as a function of the square root of imbibition time. (c) Imbibition lengths extracted via the optical reflection method at selected times. The dashed line is a guide for the eye. The extracted effective viscosity, $η_{eff}$ , in the two regimes is4660 Pa s (magenta) and 910 Pa s (green) for regimes I and II, respectively. The solid black line is the prediction of LWE. The calculation is based on the bulk viscosity $η_{0} (bulk) = 285 Pa s$ ; $γ_{L} = 30.1 mN / m$ ; $\cos θ = 0.88$ ; $R = 20 nm$ .
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Figure 4
Schematic of PI imbibition in native nanopores. Four colored chains are shown at initial (left) and additional chains at later stages (right). Initially only a small number of segments corresponding to the red chain are adsorbed to the walls forming some trains, loops and tails. At latter stages, additional chains have segments in the vicinity of the pore walls and inner chains (e.g., yellow chain) are more entangled with the loops of the adsorbed chains (red or blue chains).
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