Liquid chromatography of macromolecules at the critical adsorption point. II. Role of column packing: Bare silica gel

Berek, Dušan; Jančo, Miroslav; Meira, G. R.

doi:10.1002/(sici)1099-0518(19980715)36:9<1363::aid-pola3>3.0.co;2-u

Cited by 68 publications

(73 citation statements)

References 6 publications

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“…Values of the binary g 12 , g 13 and g 23 , and of the ternary, g T , interaction functions composition dependent for the different systems studied, obtained from ref. [19 -21] System g 12 4) Excepting in extreme conditions, such as b 3 a 0.01 and b 2 A 0.05, the expected behavior is observed, that is the crosslinking degree increases as the gel volume fraction does (according to Equation (8)- (12)). Therefore, from a SEC experiment where a polymeric solute (at a given b 2 ) + solvent elutes in two different cross-linked networks of the same chemical nature and characteristics (here PS/DVB), it will be possible to calculate their respective crosslinking degrees in order to asses or judge the quality of both packings.…”

Section: Crosslinking Degree Of Gelsmentioning

confidence: 99%

“…As seen, for a given gel with v N A V 0 constant, the swelling degree increases (lower b 3 ) as the solvent is better for the network, that is, as the solvent-gel interaction parameter, v 13 , and the solvent molar volume decrease (see Table 1), in good agreement with the expected from Equation (12).…”

Section: Crosslinking Degree Of Gelsmentioning

confidence: 99%

“…Both equations predict appropriately the chromatographic behavior of crosslinked polymers in the presence of binary solvents (Equation (8)) or in pure solvent (Equation (9)), respectively, as it will be shown later on in the Results Section. Furthermore, Equation (11) and (12) allow to evaluate either the chain density or the interaction parameter, v 13 , if previously the swelling degree (b À1…”

Section: Introductionmentioning

confidence: 99%

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Quantitative Evaluation of the Swelling and Crosslinking Degrees in Two Organic Gel Packings for SEC

Garcı́a

Recalde

Figueruelo

et al. 2001

Macromol. Chem. Phys.

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The elution behavior of different solvent/polymer systems has been studied by means of size‐exclusion chromatography (SEC) in two organic column packings based on polystyrene/divinylbenzene (PS/DVB) copolymer, named μ‐styragel and TSK‐Gel HHR. Both packings offer similar characteristics (pore size, particle size, efficiency) but some differences arise when eluting the same systems. The different elution behavior observed in both polymeric gels has been analyzed in terms of their swelling and crosslinking degrees. To evaluate the magnitude of these parameters, a new equation is proposed which has been derived from the Flory‐Huggins theory of swelling equilibrium, and takes into account binary and ternary thermodynamic interaction functions. The equation appropriately predicts the experimental results, showing that the gel that exhibits more solute‐packing attractive interactions (or adsorption as secondary mechanism) is also the one with the highest crosslinking degree or lowest swelling ratio. In this sense, the μ‐styragel column was the most crosslinked polymer network. In addition, the influence of solvent nature, polymer nature, and solute composition on the observed swelling degree has also been compared in both packings.

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Section: Crosslinking Degree Of Gelsmentioning

confidence: 99%

Section: Crosslinking Degree Of Gelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Quantitative Evaluation of the Swelling and Crosslinking Degrees in Two Organic Gel Packings for SEC

Garcı́a

Recalde

Figueruelo

et al. 2001

Macromol. Chem. Phys.

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“…[1][2][3][4][5] Their goal is the suppression of the molar mass effect on retention of one kind of polymer species while allowing free elution and, thus, the separation of other kinds of macromolecules. In contrast to a better known isocratic liquid chromatography under critical conditions (LC CC), [6][7][8][9] the LC LC methods employ a local gradient that is a ''barrier'' approach. Macromolecules eluting under LC CC conditions are in a quasi-static equilibrium with both their solvent and the column packing.…”

Section: Introductionmentioning

confidence: 99%

Liquid Chromatography of Polymers under Limiting Conditions of Desorption, 3

Šnauko

Berek

2005

Macro Chemistry & Physics

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Summary: Liquid chromatography under limiting conditions of desorption (LC LCD) enables the elution of adsorbing macromolecules independent of their size in solution. In this way, polymer species with different adsorptivities can be separated without mutual interference. It is shown on systems of bare silica gel, a tetrahydrofuran/toluene‐mixed eluent and poly(methyl methacrylate)s (PMMA) that LC LCD produces narrow, focused peaks with retention volumes independent of not only polymer molar mass but also, to a large extent, the concentration and volume of the injected sample. Sample capacity of LC LCD is very high, and sample volume can reach as much as 80% of the column pore volume. Reduced sample dilution or even its re‐concentration within the column is important for two‐dimensional separations. Changes in temperature as large as 40 °C only slightly affected retention volumes of the LC LCD‐eluted PMMA. Consequently, the LC LCD method is rather robust and user‐friendly. A practical application of LC LCD for the separation of model polymer blends has been demonstrated. Polystyrene and PMMA of similar molar masses were easily separated in less than four minutes using a small LC LCD column of low efficiency. The LC LCD fractions were successively transported into an on‐line SEC column either directly or after storage in the LC LCD column. The SEC system was equipped with a refractive index detector and a multi‐angle light scattering (MALS) detector. The MALS detector proved a good reproducibility of the molar masses for polymer blend components determined with a combination of LC LCD and SEC. Storage of the fractions within the LC LCD column even for several hours exhibited only a negligible effect on the determined molar mass averages.Scheme of the two‐dimensional chromatograph used. The capillary resistor had a flow resistance similar to that of the SEC column. For further details, see text.imageScheme of the two‐dimensional chromatograph used. The capillary resistor had a flow resistance similar to that of the SEC column. For further details, see text.

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“…17,18 Eventually, fractions of PEMA produced by SEC were on line separated according to their streoregularity with help of LC CC. Unfortunately, LC CC suffers from several drawbacks, such as -high sensitivity of many LC CC chromatographic systems toward small variations of experimental conditions, especially to fluctuations in the eluent composition, pressure, and temperature, as well as to changes in the column interactivity 19,20 -extensive broadening of the chromatographic zones [19][20][21] -reduced recovery of polymers with increased molar mass; this makes LC CC hardly applicable to molar masses over 100 kgÁmol À1 . [21][22][23][24][25] The latter shortage may also bias the EG LC separations.…”

mentioning

confidence: 98%

Liquid Chromatography under Limiting Conditions of Desorption IV. Separation of Macromolecules According to Their Stereoregularity

et al. 2009

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Liquid chromatography under limiting conditions of adsorption (LC LCD) is a novel technique for separation of polymers that exhibit different extent of adsorption on the porous column packing of appropriate polarity. LC LCD is based on the selective ''barrier effect'' induced by a narrow zone of the adsorption promoting liquid that is introduced into column in front of separated macromolecules of different nature. The small molecules that form the barrier elute slowly because they permeate the packing pores. The partially or fully pore excluded polymer molecules elute rapidly. The barrier hinders fast elution of macromolecules that tend to be adsorbed within column packing; their elution is slowed down. At the same time, the non-adsorbed polymer species elute non-hindered. It is shown that due to the controlled barrier effect even a very small difference in the extent of adsorption between isotactic and syndiotactic macromolecules of poly(methacrylate)s can lead to the significant distinction in their retention volumes. While the direct LC LCD separation of poly(methyl methacrylate)s of different stereoregularity is often precluded by the aggregation of unlike macromolecules, the highly stereoregular poly(ethyl methacrylate)s of distinct kind can be easily discriminated irrespective of their molar mass. Simultaneously, the low molecular and oligomeric impurities can be removed and, if necessary they can be identified and quantified by independent methods. In this way, LC LCD can assist purification of stereoregular polymers and serve as the first step in the twodimensional liquid chromatography of their non-aggregated mixtures.

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Liquid chromatography of macromolecules at the critical adsorption point. II. Role of column packing: Bare silica gel

Cited by 68 publications

References 6 publications

Quantitative Evaluation of the Swelling and Crosslinking Degrees in Two Organic Gel Packings for SEC

Quantitative Evaluation of the Swelling and Crosslinking Degrees in Two Organic Gel Packings for SEC

Liquid Chromatography of Polymers under Limiting Conditions of Desorption, 3

Liquid Chromatography under Limiting Conditions of Desorption IV. Separation of Macromolecules According to Their Stereoregularity

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