Charge Regulation Stabilizes the Formation of Ionic Liquid-Based Amphiphilic Oligomer Droplet Interface Bilayers

Zening Liu; Graham J. Taylor; Yingdong Luo; Kunlun Hong; Robert L. Sacci; John Katsaras; Jan Michael Carrillo; Benjamin Doughty; Charles Patrick Collier

doi:10.1002/macp.202400337

Charge Regulation Stabilizes the Formation of Ionic Liquid-Based Amphiphilic Oligomer Droplet Interface Bilayers

Zening Liu, Graham J. Taylor, Yingdong Luo, Kunlun Hong, Robert L. Sacci, John Katsaras, Jan Michael Carrillo, Benjamin Doughty, Charles Patrick Collier

Research output: Contribution to journal › Article › peer-review

1 Scopus citations

Abstract

Amphiphilic charged oligomers (oligodimethylsiloxane – methylimidazolium cation, ODMS-MIM ⁽⁺⁾), assemble into bilayers using the droplet interface bilayer (DIB) platform, possess similar size and functionality as phospholipid bilayers, but exhibit increased stability. The oligomer ionic headgroups (MIM⁽⁺⁾) are covalently bound to monodisperse, short-chain (n = 13) hydrophobic tails (ODMS). These self-assemble as monolayer brushes at the oil–aqueous interface of water droplets that are influenced by both the charged cationic headgroups, and the nature of the covalently attached tails in the organic phase. Charge regulation (CR) stabilizes the formation of ordered, molecularly close-packed brush phases, which results in highly insulating, stable DIB membranes, with contributions from specific ion-pairing effects, Debye screening, and voltage-dependent electrocompressive stresses. In the oil phase, interactions between hexadecane, a good solvent for ODMS, and the hydrophobic tails result in extended waiting times for bilayer formation compared to phospholipid DIBs, for which hexadecane is a poor solvent. Close agreement between experimental values and predictions for two key parameters, the critical membrane thickness, h_c, and maximal grafted headgroup density, Γ₀, validate an electrostatic CR model consisting of adsorption and partial neutralization of counterions at a charged interface.

Original language	English
Article number	2400337
Journal	Macromolecular Chemistry and Physics
Volume	226
Issue number	12
DOIs	https://doi.org/10.1002/macp.202400337
State	Published - Jun 20 2025

Funding

This manuscript was authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so, for the United States Government purposes. B.D. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. R.L.S. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. J.K. was supported through the Scientific User Facilities Division of the Department of Energy, Office of Science, sponsored by the Basic Energy Science Program, DOE Office of Science, under Contract No. DEAC05-00OR22725. K.H., J.-M.C., Z.L., G.T., and C.P.C. performed work at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility and sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. This manuscript was authored by UT\u2010Battelle, LLC, under Contract No. DE\u2010AC0500OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid\u2010up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so, for the United States Government purposes. B.D. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. R.L.S. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. J.K. was supported through the Scientific User Facilities Division of the Department of Energy, Office of Science, sponsored by the Basic Energy Science Program, DOE Office of Science, under Contract No. DEAC05\u201000OR22725. K.H., J.\u2010M.C., Z.L., G.T., and C.P.C. performed work at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility and sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

Keywords

charge regulation
droplet interface bilayers
ionic polymer stabilized interface
neuromorphic devices

Access to Document

10.1002/macp.202400337

Cite this

@article{3c74c1e4fb8f45289d37d9f811948726,

title = "Charge Regulation Stabilizes the Formation of Ionic Liquid-Based Amphiphilic Oligomer Droplet Interface Bilayers",

abstract = "Amphiphilic charged oligomers (oligodimethylsiloxane – methylimidazolium cation, ODMS-MIM (+)), assemble into bilayers using the droplet interface bilayer (DIB) platform, possess similar size and functionality as phospholipid bilayers, but exhibit increased stability. The oligomer ionic headgroups (MIM(+)) are covalently bound to monodisperse, short-chain (n = 13) hydrophobic tails (ODMS). These self-assemble as monolayer brushes at the oil–aqueous interface of water droplets that are influenced by both the charged cationic headgroups, and the nature of the covalently attached tails in the organic phase. Charge regulation (CR) stabilizes the formation of ordered, molecularly close-packed brush phases, which results in highly insulating, stable DIB membranes, with contributions from specific ion-pairing effects, Debye screening, and voltage-dependent electrocompressive stresses. In the oil phase, interactions between hexadecane, a good solvent for ODMS, and the hydrophobic tails result in extended waiting times for bilayer formation compared to phospholipid DIBs, for which hexadecane is a poor solvent. Close agreement between experimental values and predictions for two key parameters, the critical membrane thickness, hc, and maximal grafted headgroup density, Γ0, validate an electrostatic CR model consisting of adsorption and partial neutralization of counterions at a charged interface.",

keywords = "charge regulation, droplet interface bilayers, ionic polymer stabilized interface, neuromorphic devices",

author = "Zening Liu and Taylor, \{Graham J.\} and Yingdong Luo and Kunlun Hong and Sacci, \{Robert L.\} and John Katsaras and Carrillo, \{Jan Michael\} and Benjamin Doughty and Collier, \{Charles Patrick\}",

note = "Publisher Copyright: {\textcopyright} 2025 The Author(s). Macromolecular Chemistry and Physics published by Wiley-VCH GmbH.",

year = "2025",

month = jun,

day = "20",

doi = "10.1002/macp.202400337",

language = "English",

volume = "226",

journal = "Macromolecular Chemistry and Physics",

issn = "1022-1352",

publisher = "wiley",

number = "12",

}

TY - JOUR

T1 - Charge Regulation Stabilizes the Formation of Ionic Liquid-Based Amphiphilic Oligomer Droplet Interface Bilayers

AU - Liu, Zening

AU - Taylor, Graham J.

AU - Luo, Yingdong

AU - Hong, Kunlun

AU - Sacci, Robert L.

AU - Katsaras, John

AU - Carrillo, Jan Michael

AU - Doughty, Benjamin

AU - Collier, Charles Patrick

PY - 2025/6/20

Y1 - 2025/6/20

N2 - Amphiphilic charged oligomers (oligodimethylsiloxane – methylimidazolium cation, ODMS-MIM (+)), assemble into bilayers using the droplet interface bilayer (DIB) platform, possess similar size and functionality as phospholipid bilayers, but exhibit increased stability. The oligomer ionic headgroups (MIM(+)) are covalently bound to monodisperse, short-chain (n = 13) hydrophobic tails (ODMS). These self-assemble as monolayer brushes at the oil–aqueous interface of water droplets that are influenced by both the charged cationic headgroups, and the nature of the covalently attached tails in the organic phase. Charge regulation (CR) stabilizes the formation of ordered, molecularly close-packed brush phases, which results in highly insulating, stable DIB membranes, with contributions from specific ion-pairing effects, Debye screening, and voltage-dependent electrocompressive stresses. In the oil phase, interactions between hexadecane, a good solvent for ODMS, and the hydrophobic tails result in extended waiting times for bilayer formation compared to phospholipid DIBs, for which hexadecane is a poor solvent. Close agreement between experimental values and predictions for two key parameters, the critical membrane thickness, hc, and maximal grafted headgroup density, Γ0, validate an electrostatic CR model consisting of adsorption and partial neutralization of counterions at a charged interface.

AB - Amphiphilic charged oligomers (oligodimethylsiloxane – methylimidazolium cation, ODMS-MIM (+)), assemble into bilayers using the droplet interface bilayer (DIB) platform, possess similar size and functionality as phospholipid bilayers, but exhibit increased stability. The oligomer ionic headgroups (MIM(+)) are covalently bound to monodisperse, short-chain (n = 13) hydrophobic tails (ODMS). These self-assemble as monolayer brushes at the oil–aqueous interface of water droplets that are influenced by both the charged cationic headgroups, and the nature of the covalently attached tails in the organic phase. Charge regulation (CR) stabilizes the formation of ordered, molecularly close-packed brush phases, which results in highly insulating, stable DIB membranes, with contributions from specific ion-pairing effects, Debye screening, and voltage-dependent electrocompressive stresses. In the oil phase, interactions between hexadecane, a good solvent for ODMS, and the hydrophobic tails result in extended waiting times for bilayer formation compared to phospholipid DIBs, for which hexadecane is a poor solvent. Close agreement between experimental values and predictions for two key parameters, the critical membrane thickness, hc, and maximal grafted headgroup density, Γ0, validate an electrostatic CR model consisting of adsorption and partial neutralization of counterions at a charged interface.

KW - charge regulation

KW - droplet interface bilayers

KW - ionic polymer stabilized interface

KW - neuromorphic devices

UR - http://www.scopus.com/inward/record.url?scp=105002214118&partnerID=8YFLogxK

U2 - 10.1002/macp.202400337

DO - 10.1002/macp.202400337

M3 - Article

AN - SCOPUS:105002214118

SN - 1022-1352

VL - 226

JO - Macromolecular Chemistry and Physics

JF - Macromolecular Chemistry and Physics

IS - 12

M1 - 2400337

ER -

Charge Regulation Stabilizes the Formation of Ionic Liquid-Based Amphiphilic Oligomer Droplet Interface Bilayers

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this