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Using EPR spectroscopy as a unique probe of molecular-scale reorganization and solvation in self-assembled gel-phase materials

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Using EPR spectroscopy as a unique probe of molecular-scale reorganization and solvation in self-assembled gel-phase materials. / Caragheorgheopol, Agneta; Edwards, William; Hardy, John G.; Smith, David K.; Chechik, Victor.

In: Langmuir, Vol. 30, No. 30, 13.07.2014, p. 9210-9218.

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Caragheorgheopol, Agneta ; Edwards, William ; Hardy, John G. ; Smith, David K. ; Chechik, Victor. / Using EPR spectroscopy as a unique probe of molecular-scale reorganization and solvation in self-assembled gel-phase materials. In: Langmuir. 2014 ; Vol. 30, No. 30. pp. 9210-9218.

Bibtex

@article{49af98fdd816418e9aa2123c08203f0c,
title = "Using EPR spectroscopy as a unique probe of molecular-scale reorganization and solvation in self-assembled gel-phase materials",
abstract = "We describe the synthesis of spin-labeled bis-ureas which coassemble with bis-urea gelators and report on self-assembly as detected using electron paramagnetic resonance spectroscopy (EPR). Specifically, EPR detects the gel-sol transition and allows us to quantify how much spin-label is immobilized within the gel fibers and how much is present in mobile solvent pools-as controlled by temperature, gelator structure, and thermal history. EPR is also able to report on the initial self-assembly processes below the gelation threshold which are not macroscopically visible and appears to be more sensitive than NMR to intermediate-sized nongelating oligomeric species. By studying dilute solutions of gelator molecules and using either single or double spin-labels, EPR allows quantification of the initial steps of the hierarchical self-assembly process in terms of cooperativity and association constant. Finally, EPR enables us to estimate the degree of gel-fiber solvation by probing the distances between spin-labels. Comparison of experimental data against the predicted distances assuming the nanofibers are only composed of gelator molecules indicates a significant difference, which can be assigned to the presence of a quantifiable number of explicit solvent molecules. In summary, EPR provides unique data and yields powerful insight into how molecular-scale mobility and solvation impact on assembly of supramolecular gels.",
keywords = "SUPRAMOLECULAR ARCHITECTURES, ORGANOGEL FORMATION, WEIGHT GELATORS, SPIN LABELS, SOLVENT, GELATION, SOLUBILITY, POLYMERIZATION, PARAMETERS, HYDROGELS, Chemistry(all), Materials Science(all)",
author = "Agneta Caragheorgheopol and William Edwards and Hardy, {John G.} and Smith, {David K.} and Victor Chechik",
year = "2014",
month = jul,
day = "13",
doi = "10.1021/la501641q",
language = "English",
volume = "30",
pages = "9210--9218",
journal = "Langmuir",
issn = "0743-7463",
publisher = "AMER CHEMICAL SOC",
number = "30",

}

RIS

TY - JOUR

T1 - Using EPR spectroscopy as a unique probe of molecular-scale reorganization and solvation in self-assembled gel-phase materials

AU - Caragheorgheopol, Agneta

AU - Edwards, William

AU - Hardy, John G.

AU - Smith, David K.

AU - Chechik, Victor

PY - 2014/7/13

Y1 - 2014/7/13

N2 - We describe the synthesis of spin-labeled bis-ureas which coassemble with bis-urea gelators and report on self-assembly as detected using electron paramagnetic resonance spectroscopy (EPR). Specifically, EPR detects the gel-sol transition and allows us to quantify how much spin-label is immobilized within the gel fibers and how much is present in mobile solvent pools-as controlled by temperature, gelator structure, and thermal history. EPR is also able to report on the initial self-assembly processes below the gelation threshold which are not macroscopically visible and appears to be more sensitive than NMR to intermediate-sized nongelating oligomeric species. By studying dilute solutions of gelator molecules and using either single or double spin-labels, EPR allows quantification of the initial steps of the hierarchical self-assembly process in terms of cooperativity and association constant. Finally, EPR enables us to estimate the degree of gel-fiber solvation by probing the distances between spin-labels. Comparison of experimental data against the predicted distances assuming the nanofibers are only composed of gelator molecules indicates a significant difference, which can be assigned to the presence of a quantifiable number of explicit solvent molecules. In summary, EPR provides unique data and yields powerful insight into how molecular-scale mobility and solvation impact on assembly of supramolecular gels.

AB - We describe the synthesis of spin-labeled bis-ureas which coassemble with bis-urea gelators and report on self-assembly as detected using electron paramagnetic resonance spectroscopy (EPR). Specifically, EPR detects the gel-sol transition and allows us to quantify how much spin-label is immobilized within the gel fibers and how much is present in mobile solvent pools-as controlled by temperature, gelator structure, and thermal history. EPR is also able to report on the initial self-assembly processes below the gelation threshold which are not macroscopically visible and appears to be more sensitive than NMR to intermediate-sized nongelating oligomeric species. By studying dilute solutions of gelator molecules and using either single or double spin-labels, EPR allows quantification of the initial steps of the hierarchical self-assembly process in terms of cooperativity and association constant. Finally, EPR enables us to estimate the degree of gel-fiber solvation by probing the distances between spin-labels. Comparison of experimental data against the predicted distances assuming the nanofibers are only composed of gelator molecules indicates a significant difference, which can be assigned to the presence of a quantifiable number of explicit solvent molecules. In summary, EPR provides unique data and yields powerful insight into how molecular-scale mobility and solvation impact on assembly of supramolecular gels.

KW - SUPRAMOLECULAR ARCHITECTURES

KW - ORGANOGEL FORMATION

KW - WEIGHT GELATORS

KW - SPIN LABELS

KW - SOLVENT

KW - GELATION

KW - SOLUBILITY

KW - POLYMERIZATION

KW - PARAMETERS

KW - HYDROGELS

KW - Chemistry(all)

KW - Materials Science(all)

U2 - 10.1021/la501641q

DO - 10.1021/la501641q

M3 - Journal article

VL - 30

SP - 9210

EP - 9218

JO - Langmuir

JF - Langmuir

SN - 0743-7463

IS - 30

ER -