Experimental verification of the concept of chromatographic “invisibility” in critical chromatography of block copolymers

Zimina, Tatiana M.; Kever, Ye.Ye.; Melenevskaya, Ye.Yu.; Zgonnik, V. N.; Belen'kii, B.G.

doi:10.1016/0032-3950(91)90235-i

Cited by 10 publications

(13 citation statements)

References 5 publications

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“…As a result, the molar mass of the SEC eluted blocks can be determined as if the ''critically'' eluted blocks were not present. [8][9][10][11] It seems however that this approach suffers from some limitations. [12,13] Still, LC CC can efficiently separate the parent homopolymer eluted under critical conditions, for example poly(X) from the diblock copolymer of the poly(X)-block-poly(Y) type.…”

Section: Introductionmentioning

confidence: 99%

Separation of Parent Homopolymers from Diblock Copolymers by Liquid Chromatography under Limiting Conditions of Desorption, 2 ‐ Optimization of Experimental Arrangement

Berek¹

2008

Macro Chemistry & Physics

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The experimental arrangement for liquid chromatography under limiting conditions of desorption was optimized, aiming at separation of the parent homopolymers from diblock copolymers. Measurements with the block copolymer PS‐b‐PMMA have confirmed that the method enables fast and efficient separation of both parent homopolymers PS and PMMA from the copolymers in a single run. The new experimental set‐up also allows the separation of potentially present low molecular or oligomeric admixtures from the polymeric constituents of sample. The peak broadening of the non‐retained macromolecules has been suppressed. The sample recovery is high and can be easily checked by the injection of a large volume of an appropriate displacer.

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Section: Introductionmentioning

confidence: 99%

Separation of Parent Homopolymers from Diblock Copolymers by Liquid Chromatography under Limiting Conditions of Desorption, 2 ‐ Optimization of Experimental Arrangement

Berek¹

2008

Macro Chemistry & Physics

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“…Zimina et al. noticed the harmful effect of the band broadening in LC CC of block copolymers already in their first paper . Their observation was confirmed by numerous authors.…”

Section: Coupled Lc Methodsmentioning

confidence: 84%

“…This ingenious idea was for the first time in practice employed by Zimina et al. and afterward by numerous other authors . Later, some uncertainty was expressed concerning straightforward universal applicability of LC CC for molecular characterization of complex polymers including determination of molar mass average and dispersity of the noninteractive blocks in diblock copolymers , however they mostly remained overlooked.…”

Section: Coupled Lc Methodsmentioning

confidence: 99%

Critical assessment of “critical” liquid chromatography of block copolymers

Berek

2016

J of Separation Science

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Brief elucidation is presented of potential difficulties the researcher can face in the course of the molecular characterization of block copolymers with help of liquid chromatography under critical conditions. The impediments include the demanding identification of critical conditions, the limited area of applicable polymer molar mass, the high sensitivity of critical conditions toward minute changes in experimental conditions including changes in the interactivity of the column packing, extensive band broadening, limited sample recovery, pressure effects, detection problems, coelution of block copolymers with their noninteractive parent homopolymers, possible effect of the noninteracting chains of block copolymers on the behavior of the interacting blocks, and role of preferential solvation of macromolecules in mixed solvents. These matters may complicate proper data evaluation and challenge the exactness of results obtained. Special attention is paid to the so far neglected phenomena of preferential solvation, which may affect not only detection of block copolymers but also their retention. The latter occurrence is demonstrated by the behavior of both poly(methyl methacrylate)s eluted from bare silica gel in a mixed eluent tetrahydrofuran plus toluene and polystyrenes eluted from silica gel C18 bonded phase with the mobile phase of tetrahydrofuran/n-hexane.

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“…The real, acting critical composition of eluent may be, and likely is, the composition somewhere, in the middle, of the solvent peak. The presence of the solvent peak influences especially pronouncedly the elu- The disruption of the polymer separation by the solvent peak may be the reason why broad and narrow polymer standards did not elute under the critical conditions as a very narrow peak, as has been observed by the first critical conditions investigators and, subsequently, by others [7,21,56,62,79]. Namely, CEEC should yield a very narrow peaks for polymeric samples of different polydispersity, with the width of the polymeric peak determined only by the chromatographic efficiency of LC column.…”

Section: Polymer Peaks and Solvent Peaks Under Critical Conditionsmentioning

confidence: 84%

“…Under critical conditions for one homopolymer, which constitutes a part of a binary copolymer, a second polymer may be characterized [61][62][63][64]80,176]. The molar mass of a part of copolymer, which is not under critical conditions, however, is [57].…”

Section: Comparison Of Molar Masses Calculated From Separation Under mentioning

confidence: 99%

Liquid Chromatography under Critical and Limiting Conditions: A Survey of Experimental Systems for Synthetic Polymers

Macko

Hunkeler

2003

Liquid Chromatography / FTIR Microspectroscopy / Microwave Assisted Synthesis

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At the interface between the entropic size exclusion separation and the enthalpydominated liquid adsorption chromatography it is possible, experimentally, to identify conditions where polymer samples elute independent of their molar mass. These "critical conditions" function according to theory by compensating the entropy and enthalpy of the separation. For a series of common and specialty polymers, the mobile phase compositions and temperature which provide the molar mass independent elution behavior, for a given stationary phase, have been extracted from literature and summarized herein. This collection may help to select, or forecast, suitable LC systems, when an application of liquid chromatography under critical conditions for a polymer is required. Correlations between properties of solvents, sorbents and polymers, such as solubility parameters, eluotropic strength and Mark-Houwink constants have been extracted from the collected data. Specifically, solubity parameters of critical mobile phases corresponding to a pair polymer-sorbent are in a majority of cases very similar. The elution strength of the first component of a critical binary eluent correlates linearly with the volume percent of the second component, especially, when an identical silica gel is applied. However, the critical conditions are independent of the thermodynamic quality of the solvent. Under limiting conditions, the mobile phase may be even a precipitant or a strong adsorption promoting liquid for an injected polymer. Possibilities for increase of the upper molar mass separation limit are outlined and influence of sample solvent on elution behavior is described. Applications of liquid chromatography under conditions of enthalpy-entropy compensation for separation of homo-and copolymers are also, briefly, summarized.

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Experimental verification of the concept of chromatographic “invisibility” in critical chromatography of block copolymers

Cited by 10 publications

References 5 publications

Separation of Parent Homopolymers from Diblock Copolymers by Liquid Chromatography under Limiting Conditions of Desorption, 2 ‐ Optimization of Experimental Arrangement

Separation of Parent Homopolymers from Diblock Copolymers by Liquid Chromatography under Limiting Conditions of Desorption, 2 ‐ Optimization of Experimental Arrangement

Critical assessment of “critical” liquid chromatography of block copolymers

Liquid Chromatography under Critical and Limiting Conditions: A Survey of Experimental Systems for Synthetic Polymers

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