Application of <sup>1</sup>H DOSY for Facile Measurement of Polymer Molecular Weights

Li, Weibin; Chung, Hoyong; Daeffler, Christopher S.; Johnson, Jeremiah A.; Grubbs, Robert H.

doi:10.1021/ma301666x

Cited by 178 publications

(177 citation statements)

References 46 publications

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“…However, the scaling parameters of Eq. (1) specific to that polymersolvent system must be found by measuring ⟨D⟩ on fractionated samples of the polymer with known M. Therefore, currently all PGSE NMR-based methods which convert from D to M cannot independently measure the absolute molecular mass distribution [12,13,14,15,16,17,18,19,20,21,22,23,24,25].In this paper we show that ν in Eq.(1) can be directly estimated from a single PGSE experiment in which the extremity (end-group) polymer signal can be spectrally resolved by a chemical shift from the polymer main-chain signal. The scaling exponent, ν, is a measure of the polymer conformation as well as solvent quality [3,26], with bounds of ν = 1/3 for a perfectly coiled, impenetrable, polymer ball and ν = 1 for a perfectly straight polymer rod [17].…”

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confidence: 99%

Scaling exponent and dispersity of polymers in solution by diffusion NMR

Williamson

Röding

Miklavcic

et al. 2017

Journal of Colloid and Interface Science

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Molecular mass distribution measurements by pulsed gradient spin echo nuclear magnetic resonance (PGSE NMR) spectroscopy currently require prior knowledge of scaling parameters to convert from polymer self-diffusion coefficient to molecular mass. Reversing the problem, we utilize the scaling relation as prior knowledge to uncover the scaling exponent from within the PGSE data. Thus, the scaling exponent-a measure of polymer conformation and solvent quality-and the dispersity (M w /M n ) are obtainable from one simple PGSE experiment. The method utilizes constraints and parametric distribution models in a two-step fitting routine involving first the mass-weighted signal and second the number-weighted signal. The method is developed using lognormal and gamma distribution models and tested on experimental PGSE attenuation of the terminal methylene signal and on the sum of all methylene signals of polyethylene glycol in D 2 O. Scaling exponent and dispersity estimates agree with known values in the majority of instances, leading to the potential application of the method to polymers for which characterization is not possible with alternative techniques. Keywords:Pulsed gradient spin echo, pulsed field gradient, Nuclear Magnetic Resonance spectroscopy, Molecular weight distribution, Polymers, DOSY, Polydispersity Index, Self-diffusion, Molar mass, Flory exponent, Lognormal distribution, Gamma distribution, End-group analysis, Scaling law Synthetic polymers have distributions of molecular masses determined by their synthesis [1]. Measuring the molecular mass distribution rather than its average is important because the dispersity can influence polymer properties [2]. Absolute as opposed to relative measurements are needed when using polymer physics to fully realize the potential applications of a polymer [3]. Only a handful of techniques can measure the absolute molecular mass distribution [3]. The gold standard is size exclusion chromatography (SEC) using universal calibration [4], which does not always work [5,6]. New techniques must be developed to aid in the advancement of polymer science.Pulsed gradient spin echo nuclear magnetic resonance (PGSE NMR) [7,8] is a powerful technique for obtaining the distribution of polymer self-diffusion coefficients D [9], from which the distribution of molecular masses M can be obtained by the scaling law [10] ration give PGSE NMR a competitive edge with respect to SEC. Chemical shift information [7], e.g. in a diffusion ordered spectroscopy (DOSY) plot [11], provides the ability to observe chemical heterogeneity and impurity. Sample preparation generally does not require filtration because contaminates from large particles such as dust do not impact the experiment. However, the scaling parameters of Eq. (1) specific to that polymersolvent system must be found by measuring ⟨D⟩ on fractionated samples of the polymer with known M. Therefore, currently all PGSE NMR-based methods which convert from D to M cannot independently measure the absolute molecular mass distribution [...

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confidence: 99%

Scaling exponent and dispersity of polymers in solution by diffusion NMR

Williamson

Röding

Miklavcic

et al. 2017

Journal of Colloid and Interface Science

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“…This method turned out to be a facile and accurate method for determining average molecular weights. 60 Accordingly, a calibration curve corresponding to the diffusion coefficients of a series of polyacrylates derivaties of variable known molecular weights was deduced (Figure 2A). The diffusion coefficient derived from the DOSY spectrum of (3) (Figure 2B) was then introduced into the calibration curve (marked with an arrow), resulting in an estimated average molecular weight for (3) of 180 000 g/mol.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Gossypol-Cross-Linked Boronic Acid-Modified Hydrogels: A Functional Matrix for the Controlled Release of an Anticancer Drug

et al. 2015

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Anticancer drug gossypol cross-links phenylboronic acid-modified acrylamide copolymer chains to form a hydrogel matrix. The hydrogel is dissociated in an acidic environment (pH 4.5), and its dissociation is enhanced in the presence of lactic acid (an α-hydroxy carboxylic acid) as compared to formic acid. The enhanced dissociation of the hydrogel by lactic acid is attributed to the effective separation of the boronate ester bridging groups through the formation of a stabilized complex between the boronic acid substituent and the lactic acid. Because lactic acid exists in cancer cells in elevated amounts and the cancer cells' environment is acidic, the cross-linked hydrogel represents a stimuli-responsive matrix for the controlled release of gossypol. The functionality is demonstrated and characterized by rheology and other spectroscopic means.

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“…Note that the binuclear catalysts also incorporate more N(octenyl) n Pr 2 than does the mononuclear Sc1. Not unexpectedly,GPC [2a] and DOSY [20] were inconclusive in obtaining reliable ethylene + AO copolymer M n values in the present systems (see the Supporting Information for discussion, procedures,and results). Furthermore,A Oh omopolymerizations in the presence of these catalysts exhibit negligible activity under identical reaction conditions.…”

Section: Angewandte Chemiementioning

confidence: 95%

Scandium‐Catalyzed Self‐Assisted Polar Co‐monomer Enchainment in Ethylene Polymerization

et al. 2017

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Direct coordinative copolymerization of ethylene with functionalizedc o-monomers is al ong-sought-after approach to introducing polyolefin functionality.H owever, functional-group Lewis basicity typically depresses catalytic activity and co-monomer incorporation. Finding alternatives to intensively studied group 4d 0 and late-transition-metal catalysts is crucial to addressing this long-standing challenge. Shownh erein is that mono-and binuclear organoscandium complexes with ab orate cocatalyst are active for ethylene + amino olefin [AO; H 2 C=CH(CH 2 ) n NR 2 ]copolymerizations in the absence of aL ewis-acidic masking reagent. Both activity (up to 4.2 10 2 kg mol À1 ·h À1> atm À1> )a nd AO incorporation (up to 12 %a t0 .2 m [AO]) are appreciable.L inker-lengthdependent (n) AO incorporation and mechanistic probes support an unusual functional-group-assisted enchainment mechanism. Furthermore,t he binuclear catalysts exhibit enhanced AO tolerance and enhanced long chain AO incorporation.

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Application of ¹H DOSY for Facile Measurement of Polymer Molecular Weights

Cited by 178 publications

References 46 publications

Scaling exponent and dispersity of polymers in solution by diffusion NMR

Scaling exponent and dispersity of polymers in solution by diffusion NMR

Gossypol-Cross-Linked Boronic Acid-Modified Hydrogels: A Functional Matrix for the Controlled Release of an Anticancer Drug

Scandium‐Catalyzed Self‐Assisted Polar Co‐monomer Enchainment in Ethylene Polymerization

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Application of 1H DOSY for Facile Measurement of Polymer Molecular Weights

Cited by 178 publications

References 46 publications

Scaling exponent and dispersity of polymers in solution by diffusion NMR

Scaling exponent and dispersity of polymers in solution by diffusion NMR

Gossypol-Cross-Linked Boronic Acid-Modified Hydrogels: A Functional Matrix for the Controlled Release of an Anticancer Drug

Scandium‐Catalyzed Self‐Assisted Polar Co‐monomer Enchainment in Ethylene Polymerization

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Application of ¹H DOSY for Facile Measurement of Polymer Molecular Weights