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Title: Poly(ethylene glycol)s in Semidilute Regime: Radius of Gyration in the Bulk and Partitioning into a Nanopore

Abstract

In this work, using two approaches, small-angle neutron scattering (SANS) from bulk solutions and nanopore conductance-fluctuation analysis, we studied structural and dynamic features of poly(ethylene glycol) (PEG) water/salt solutions in the dilute and semidilute regimes. SANS measurements on PEG 3400 at the zero-average contrast yielded the single chain radius of gyration (R g) over 1–30 wt %. We observed a small but statistically reliable decrease in R g with increasing PEG concentration: at 30 wt % the chain contracts by a factor of 0.94. Analyzing conductance fluctuations of the α-hemolysin nanopore in the mixtures of PEG 200 with PEG 3400, we demonstrated that polymer partitioning into the nanopore is mostly due to PEG 200. Specifically, for a 1:1 wt/wt mixture the smaller polymer dominates to the extent that only about 1/25 of the nanopore volume is taken by the larger polymer. In conclusion, these findings advance our conceptual and quantitative understanding of nanopore polymer partitioning; they also support the main assumptions of the recent “polymers-pushing-polymers” model.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3]; ORCiD logo [4];  [3];  [1]
  1. Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD (United States). Section on Molecular Transport
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biology and Soft Matter Division
  3. Univ. of Massachusetts, Amherst, MA (United States). Department of Physics
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1424464
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Macromolecules
Additional Journal Information:
Journal Volume: 50; Journal Issue: 6; Journal ID: ISSN 0024-9297
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Gurnev, Philip A., Stanley, Christopher B., Aksoyoglu, M. Alphan, Hong, Kunlun, Parsegian, V. Adrian, and Bezrukov, Sergey M. Poly(ethylene glycol)s in Semidilute Regime: Radius of Gyration in the Bulk and Partitioning into a Nanopore. United States: N. p., 2017. Web. doi:10.1021/acs.macromol.6b02571.
Gurnev, Philip A., Stanley, Christopher B., Aksoyoglu, M. Alphan, Hong, Kunlun, Parsegian, V. Adrian, & Bezrukov, Sergey M. Poly(ethylene glycol)s in Semidilute Regime: Radius of Gyration in the Bulk and Partitioning into a Nanopore. United States. doi:10.1021/acs.macromol.6b02571.
Gurnev, Philip A., Stanley, Christopher B., Aksoyoglu, M. Alphan, Hong, Kunlun, Parsegian, V. Adrian, and Bezrukov, Sergey M. Thu . "Poly(ethylene glycol)s in Semidilute Regime: Radius of Gyration in the Bulk and Partitioning into a Nanopore". United States. doi:10.1021/acs.macromol.6b02571. https://www.osti.gov/servlets/purl/1424464.
@article{osti_1424464,
title = {Poly(ethylene glycol)s in Semidilute Regime: Radius of Gyration in the Bulk and Partitioning into a Nanopore},
author = {Gurnev, Philip A. and Stanley, Christopher B. and Aksoyoglu, M. Alphan and Hong, Kunlun and Parsegian, V. Adrian and Bezrukov, Sergey M.},
abstractNote = {In this work, using two approaches, small-angle neutron scattering (SANS) from bulk solutions and nanopore conductance-fluctuation analysis, we studied structural and dynamic features of poly(ethylene glycol) (PEG) water/salt solutions in the dilute and semidilute regimes. SANS measurements on PEG 3400 at the zero-average contrast yielded the single chain radius of gyration (Rg) over 1–30 wt %. We observed a small but statistically reliable decrease in Rg with increasing PEG concentration: at 30 wt % the chain contracts by a factor of 0.94. Analyzing conductance fluctuations of the α-hemolysin nanopore in the mixtures of PEG 200 with PEG 3400, we demonstrated that polymer partitioning into the nanopore is mostly due to PEG 200. Specifically, for a 1:1 wt/wt mixture the smaller polymer dominates to the extent that only about 1/25 of the nanopore volume is taken by the larger polymer. In conclusion, these findings advance our conceptual and quantitative understanding of nanopore polymer partitioning; they also support the main assumptions of the recent “polymers-pushing-polymers” model.},
doi = {10.1021/acs.macromol.6b02571},
journal = {Macromolecules},
number = 6,
volume = 50,
place = {United States},
year = {Thu Mar 09 00:00:00 EST 2017},
month = {Thu Mar 09 00:00:00 EST 2017}
}

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  • Small-angle neutron scattering is used to investigate swelling effects of polystyrene in carbon tetrachloride and cis-decalin in the semidilute regime. The observed scaling exponent m where R{sub g}{sup 2} {approximately} {phi}{sup {minus}m} was m = 0.15 {+-} 0.01 both in carbon tetrachloride and in cis-decalin at T = 180 C, which is much weaker than the theoretical prediction m = 0.25. A review of the literature has found the scaling exponent to vary from 0.1 to 0.25. Possible causes for this variation in the observed scaling exponent are discussed.
  • Ferrocene labeled monomethoxy-poly(ethylene glycol)s (MPEG) with molecular weights of 1900 and 750 were used as redox probe solutes in poly(ethylene glycol) melt solvents of molecular weight 750, 2000, and 20000. Cyclic voltammetry and chronoamperometry at microdisk electrodes were employed to measure the diffusion coefficients of the redox probes, which were independent of the probe concentration and varied between 10{sup -7} and 10{sup -10} cm{sup 2}/s. Diffusional activation barrier results also suggest that the ferrocene label does not significantly influence the diffusivity of the probe molecule in the host solvent. Activation barrier, viscosity, and ionic conductivity results show that the LiClO{submore » 4} electrolyte does not influence the diffusion barrier or viscosity as long as the ether O/Li{sup +} ratio is >=250 (ca. 0.1 M) which is still a sufficient electrolyte concentration to allow quantitative electrochemical diffusion measurements. 21 refs., 7 figs., 2 tabs.« less
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  • The removal of carbon dioxide by using chemical absorbents has been of great interest, since it was found that the global warming effect is primarily due to excessive discharge of carbon dioxide and methane. The solubility of carbon dioxide in monoethanolamine (MEA) + ethylene glycol (EG) + water and monoethanolamine (MEA) + poly(ethylene glycol) (PEG) + water has been measured at 313.2 K and at partial pressure ranges of carbon dioxide up to 2,500 kPa. The concentrations of aqueous mixtures are 15.3 mass % MEA + 15.3 mass % EG, 15.3 mass % MEA + 42.3 mass % EG, 15.3more » mass % MEA + 15.3 mass % PEG, and 15.3 mass % MEA + 42.3 mass % PEG. In each case, the solubility was represented as functions of partial pressures of carbon dioxide.« less
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