Nonadditive Ion Effects Drive Both Collapse and Swelling of Thermoresponsive Polymers in Water

Ellen E. Bruce, Pho T. Bui, Bradley A. Rogers, Paul S. Cremer, Nico F.A. Van Der Vegt

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

When a mixture of two salts in an aqueous solution contains a weakly and a strongly hydrated anion, their combined effect is nonadditive. Herein, we report such nonadditive effects on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNiPAM) for a fixed concentration of Na2SO4 and an increasing concentration of NaI. Using molecular dynamics simulations and vibrational sum frequency spectroscopy, we demonstrate that at low concentrations of the weakly hydrated anion (I-), the cations (Na+) preferentially partition to the counterion cloud around the strongly hydrated anion (SO42-), leaving I- more hydrated. However, upon further increase in the NaI concentration, this weakly hydrated anion is forced out of solution to the polymer/water interface by sulfate. Thus, the LCST behavior of PNiPAM involves competing roles for ion hydration and polymer-iodide interactions. This concept can be generally applied to mixtures containing both a strongly and a weakly hydrated anion from the Hofmeister series.

Original languageEnglish (US)
Pages (from-to)6609-6616
Number of pages8
JournalJournal of the American Chemical Society
Volume141
Issue number16
DOIs
StatePublished - Apr 24 2019

Fingerprint

Anions
Swelling
Polymers
Negative ions
Ions
Water
Temperature
Iodides
Vibrational spectra
Molecular Dynamics Simulation
Hydration
Sulfates
Molecular dynamics
Cations
Spectrum Analysis
Salts
Positive ions
Spectroscopy
Computer simulation
poly-N-isopropylacrylamide

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Bruce, Ellen E. ; Bui, Pho T. ; Rogers, Bradley A. ; Cremer, Paul S. ; Van Der Vegt, Nico F.A. / Nonadditive Ion Effects Drive Both Collapse and Swelling of Thermoresponsive Polymers in Water. In: Journal of the American Chemical Society. 2019 ; Vol. 141, No. 16. pp. 6609-6616.
@article{24e18d7e7f0249318bbb6cd24bdb47e5,
title = "Nonadditive Ion Effects Drive Both Collapse and Swelling of Thermoresponsive Polymers in Water",
abstract = "When a mixture of two salts in an aqueous solution contains a weakly and a strongly hydrated anion, their combined effect is nonadditive. Herein, we report such nonadditive effects on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNiPAM) for a fixed concentration of Na2SO4 and an increasing concentration of NaI. Using molecular dynamics simulations and vibrational sum frequency spectroscopy, we demonstrate that at low concentrations of the weakly hydrated anion (I-), the cations (Na+) preferentially partition to the counterion cloud around the strongly hydrated anion (SO42-), leaving I- more hydrated. However, upon further increase in the NaI concentration, this weakly hydrated anion is forced out of solution to the polymer/water interface by sulfate. Thus, the LCST behavior of PNiPAM involves competing roles for ion hydration and polymer-iodide interactions. This concept can be generally applied to mixtures containing both a strongly and a weakly hydrated anion from the Hofmeister series.",
author = "Bruce, {Ellen E.} and Bui, {Pho T.} and Rogers, {Bradley A.} and Cremer, {Paul S.} and {Van Der Vegt}, {Nico F.A.}",
year = "2019",
month = "4",
day = "24",
doi = "10.1021/jacs.9b00295",
language = "English (US)",
volume = "141",
pages = "6609--6616",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "16",

}

Nonadditive Ion Effects Drive Both Collapse and Swelling of Thermoresponsive Polymers in Water. / Bruce, Ellen E.; Bui, Pho T.; Rogers, Bradley A.; Cremer, Paul S.; Van Der Vegt, Nico F.A.

In: Journal of the American Chemical Society, Vol. 141, No. 16, 24.04.2019, p. 6609-6616.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Nonadditive Ion Effects Drive Both Collapse and Swelling of Thermoresponsive Polymers in Water

AU - Bruce, Ellen E.

AU - Bui, Pho T.

AU - Rogers, Bradley A.

AU - Cremer, Paul S.

AU - Van Der Vegt, Nico F.A.

PY - 2019/4/24

Y1 - 2019/4/24

N2 - When a mixture of two salts in an aqueous solution contains a weakly and a strongly hydrated anion, their combined effect is nonadditive. Herein, we report such nonadditive effects on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNiPAM) for a fixed concentration of Na2SO4 and an increasing concentration of NaI. Using molecular dynamics simulations and vibrational sum frequency spectroscopy, we demonstrate that at low concentrations of the weakly hydrated anion (I-), the cations (Na+) preferentially partition to the counterion cloud around the strongly hydrated anion (SO42-), leaving I- more hydrated. However, upon further increase in the NaI concentration, this weakly hydrated anion is forced out of solution to the polymer/water interface by sulfate. Thus, the LCST behavior of PNiPAM involves competing roles for ion hydration and polymer-iodide interactions. This concept can be generally applied to mixtures containing both a strongly and a weakly hydrated anion from the Hofmeister series.

AB - When a mixture of two salts in an aqueous solution contains a weakly and a strongly hydrated anion, their combined effect is nonadditive. Herein, we report such nonadditive effects on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNiPAM) for a fixed concentration of Na2SO4 and an increasing concentration of NaI. Using molecular dynamics simulations and vibrational sum frequency spectroscopy, we demonstrate that at low concentrations of the weakly hydrated anion (I-), the cations (Na+) preferentially partition to the counterion cloud around the strongly hydrated anion (SO42-), leaving I- more hydrated. However, upon further increase in the NaI concentration, this weakly hydrated anion is forced out of solution to the polymer/water interface by sulfate. Thus, the LCST behavior of PNiPAM involves competing roles for ion hydration and polymer-iodide interactions. This concept can be generally applied to mixtures containing both a strongly and a weakly hydrated anion from the Hofmeister series.

UR - http://www.scopus.com/inward/record.url?scp=85064993868&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85064993868&partnerID=8YFLogxK

U2 - 10.1021/jacs.9b00295

DO - 10.1021/jacs.9b00295

M3 - Article

C2 - 30919630

AN - SCOPUS:85064993868

VL - 141

SP - 6609

EP - 6616

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 16

ER -