Characterizing Hygroscopic Films of Polyzwitterions in Electric Fields Using Neutron and X-ray Reflectometries: Electrostriction or Mass Loss?

Panagiotis Christakopoulos; Hanyu Wang; Peter V. Bonnesen; Jong K. Keum; Yangyang Wang; Kunlun Hong; Bradley S. Lokitz; Mathieu Doucet; James F. Browning; Rigoberto Advincula; Rajeev Kumar

doi:10.1021/acsami.4c09938

Characterizing Hygroscopic Films of Polyzwitterions in Electric Fields Using Neutron and X-ray Reflectometries: Electrostriction or Mass Loss?

Panagiotis Christakopoulos, Hanyu Wang, Peter V. Bonnesen, Jong K. Keum, Yangyang Wang, Kunlun Hong, Bradley S. Lokitz, Mathieu Doucet, James F. Browning, Rigoberto Advincula, Rajeev Kumar

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2 Scopus citations

Abstract

We study responses of thermally annealed ultrathin films deposited on silicon substrates and containing polyzwitterions to applied electric fields by using specular neutron reflectometry (NR). In particular, we applied 7 kV under vacuum at 150 °C on the films containing poly(1-(3-sulfonatopropyl)-2-vinylpyridinium) (P2VPPS) and its blends with either a deuterated ionic liquid (EMIMBF₄-d₁₁), potassium bromide (KBr), or deuterated sodium polystyrenesulfonate (NaPSS-d₇). The voltage was applied over an air gap, and the in situ neutron reflectivity measurements allowed us to measure changes in the films. In all the cases, we measured decreases in thicknesses of the films, which varied up to ∼8% depending on the added salt. Posteriori X-ray reflectivity (XRR) measurements on the same films at room temperature reveal that these films were highly hygroscopic, which led to the presence of water in these films. Analysis of the NR and the XRR revealed that the decrease in the thickness of the films in the neutron reflectivity experiments on heating resulted from the loss of water and the ionic liquid but not from electrostrictive effects. The in situ NR and posteriori XRR experiments revealed not only the hygroscopic nature of these films but also depth-resolved structural rearrangements due to the applied electric fields in the films containing electrolytes and polyelectrolytes. This work shows that a combination of NR and XRR can be used to distinguish between mass loss and electrostriction in films containing charged polymers such as polyzwitterions.

Original language	English
Pages (from-to)	48307-48319
Number of pages	13
Journal	ACS Applied Materials and Interfaces
Volume	16
Issue number	36
DOIs	https://doi.org/10.1021/acsami.4c09938
State	Published - Sep 11 2024

Funding

This work was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. A portion of this research used resources at the SNS, a Department of Energy (DOE) Office of Science User Facility operated by ORNL. Neutron reflectometry measurements were carried out on the Liquids Reflectometer at the SNS, which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, DOE. ORNL is managed by UT-Battelle LLC for the DOE under Contract DE-AC05-00OR22725. This manuscript has been authored by UT-Battelle, LLC, under Contract DE6AC05\u201300OR22725 with the U.S. Department of Energy. The U.S. government is authorized to reproduce and distribute reprints for government purposes notwithstanding any copyright notation hereon. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-publicaccess-plan ).

Keywords

X-ray reflectometry
deuteration
electrostriction
hygroscopic
ionic liquids
neutron reflectometry
polyzwitterions

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10.1021/acsami.4c09938

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Christakopoulos, P., Wang, H., Bonnesen, P. V., Keum, J. K., Wang, Y., Hong, K., Lokitz, B. S., Doucet, M., Browning, J. F., Advincula, R., & Kumar, R. (2024). Characterizing Hygroscopic Films of Polyzwitterions in Electric Fields Using Neutron and X-ray Reflectometries: Electrostriction or Mass Loss? ACS Applied Materials and Interfaces, 16(36), 48307-48319. https://doi.org/10.1021/acsami.4c09938

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title = "Characterizing Hygroscopic Films of Polyzwitterions in Electric Fields Using Neutron and X-ray Reflectometries: Electrostriction or Mass Loss?",

abstract = "We study responses of thermally annealed ultrathin films deposited on silicon substrates and containing polyzwitterions to applied electric fields by using specular neutron reflectometry (NR). In particular, we applied 7 kV under vacuum at 150 °C on the films containing poly(1-(3-sulfonatopropyl)-2-vinylpyridinium) (P2VPPS) and its blends with either a deuterated ionic liquid (EMIMBF4-d11), potassium bromide (KBr), or deuterated sodium polystyrenesulfonate (NaPSS-d7). The voltage was applied over an air gap, and the in situ neutron reflectivity measurements allowed us to measure changes in the films. In all the cases, we measured decreases in thicknesses of the films, which varied up to ∼8% depending on the added salt. Posteriori X-ray reflectivity (XRR) measurements on the same films at room temperature reveal that these films were highly hygroscopic, which led to the presence of water in these films. Analysis of the NR and the XRR revealed that the decrease in the thickness of the films in the neutron reflectivity experiments on heating resulted from the loss of water and the ionic liquid but not from electrostrictive effects. The in situ NR and posteriori XRR experiments revealed not only the hygroscopic nature of these films but also depth-resolved structural rearrangements due to the applied electric fields in the films containing electrolytes and polyelectrolytes. This work shows that a combination of NR and XRR can be used to distinguish between mass loss and electrostriction in films containing charged polymers such as polyzwitterions.",

keywords = "X-ray reflectometry, deuteration, electrostriction, hygroscopic, ionic liquids, neutron reflectometry, polyzwitterions",

author = "Panagiotis Christakopoulos and Hanyu Wang and Bonnesen, {Peter V.} and Keum, {Jong K.} and Yangyang Wang and Kunlun Hong and Lokitz, {Bradley S.} and Mathieu Doucet and Browning, {James F.} and Rigoberto Advincula and Rajeev Kumar",

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doi = "10.1021/acsami.4c09938",

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Christakopoulos, P , Wang, H , Bonnesen, PV , Keum, JK , Wang, Y, Hong, K, Lokitz, BS , Doucet, M , Browning, JF, Advincula, R & Kumar, R 2024, 'Characterizing Hygroscopic Films of Polyzwitterions in Electric Fields Using Neutron and X-ray Reflectometries: Electrostriction or Mass Loss?', ACS Applied Materials and Interfaces, vol. 16, no. 36, pp. 48307-48319. https://doi.org/10.1021/acsami.4c09938

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T1 - Characterizing Hygroscopic Films of Polyzwitterions in Electric Fields Using Neutron and X-ray Reflectometries

T2 - Electrostriction or Mass Loss?

AU - Christakopoulos, Panagiotis

AU - Wang, Hanyu

AU - Bonnesen, Peter V.

AU - Keum, Jong K.

AU - Wang, Yangyang

AU - Hong, Kunlun

AU - Lokitz, Bradley S.

AU - Doucet, Mathieu

AU - Browning, James F.

AU - Advincula, Rigoberto

AU - Kumar, Rajeev

PY - 2024/9/11

Y1 - 2024/9/11

N2 - We study responses of thermally annealed ultrathin films deposited on silicon substrates and containing polyzwitterions to applied electric fields by using specular neutron reflectometry (NR). In particular, we applied 7 kV under vacuum at 150 °C on the films containing poly(1-(3-sulfonatopropyl)-2-vinylpyridinium) (P2VPPS) and its blends with either a deuterated ionic liquid (EMIMBF4-d11), potassium bromide (KBr), or deuterated sodium polystyrenesulfonate (NaPSS-d7). The voltage was applied over an air gap, and the in situ neutron reflectivity measurements allowed us to measure changes in the films. In all the cases, we measured decreases in thicknesses of the films, which varied up to ∼8% depending on the added salt. Posteriori X-ray reflectivity (XRR) measurements on the same films at room temperature reveal that these films were highly hygroscopic, which led to the presence of water in these films. Analysis of the NR and the XRR revealed that the decrease in the thickness of the films in the neutron reflectivity experiments on heating resulted from the loss of water and the ionic liquid but not from electrostrictive effects. The in situ NR and posteriori XRR experiments revealed not only the hygroscopic nature of these films but also depth-resolved structural rearrangements due to the applied electric fields in the films containing electrolytes and polyelectrolytes. This work shows that a combination of NR and XRR can be used to distinguish between mass loss and electrostriction in films containing charged polymers such as polyzwitterions.

AB - We study responses of thermally annealed ultrathin films deposited on silicon substrates and containing polyzwitterions to applied electric fields by using specular neutron reflectometry (NR). In particular, we applied 7 kV under vacuum at 150 °C on the films containing poly(1-(3-sulfonatopropyl)-2-vinylpyridinium) (P2VPPS) and its blends with either a deuterated ionic liquid (EMIMBF4-d11), potassium bromide (KBr), or deuterated sodium polystyrenesulfonate (NaPSS-d7). The voltage was applied over an air gap, and the in situ neutron reflectivity measurements allowed us to measure changes in the films. In all the cases, we measured decreases in thicknesses of the films, which varied up to ∼8% depending on the added salt. Posteriori X-ray reflectivity (XRR) measurements on the same films at room temperature reveal that these films were highly hygroscopic, which led to the presence of water in these films. Analysis of the NR and the XRR revealed that the decrease in the thickness of the films in the neutron reflectivity experiments on heating resulted from the loss of water and the ionic liquid but not from electrostrictive effects. The in situ NR and posteriori XRR experiments revealed not only the hygroscopic nature of these films but also depth-resolved structural rearrangements due to the applied electric fields in the films containing electrolytes and polyelectrolytes. This work shows that a combination of NR and XRR can be used to distinguish between mass loss and electrostriction in films containing charged polymers such as polyzwitterions.

KW - X-ray reflectometry

KW - deuteration

KW - electrostriction

KW - hygroscopic

KW - ionic liquids

KW - neutron reflectometry

KW - polyzwitterions

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AN - SCOPUS:85202484979

SN - 1944-8244

VL - 16

SP - 48307

EP - 48319

JO - ACS Applied Materials and Interfaces

JF - ACS Applied Materials and Interfaces

IS - 36

ER -

Characterizing Hygroscopic Films of Polyzwitterions in Electric Fields Using Neutron and X-ray Reflectometries: Electrostriction or Mass Loss?

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