Fast determination of critical eluent composition for polymers by gradient chromatography

Bashir, Mubasher A.; Brüll, Adele; Radke, Wolfgang

doi:10.1016/j.polymer.2005.02.080

Cited by 48 publications

(25 citation statements)

References 19 publications

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“…This leads to the assumption that the lower molar mass in fraction 1 ($\overline M _{\rm n}$ = 13 kg · mol −1 ) and the absence of molar masses <10 kg · mol −1 in fraction 4 (see Figure 7) result in co‐elution of these copolymers even though they have different VA contents. The observed molar mass dependence is in agreement with the literature 26, 27…”

Section: Resultssupporting

confidence: 92%

Comparison of High‐Temperature HPLC, CRYSTAF and TREF for the Analysis of the Chemical Composition Distribution of Ethylene‐Vinyl Acetate Copolymers

Albrecht

Brüll²,

Macko

et al. 2009

Macro Chemistry & Physics

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The chemical composition distribution (CCD) is a fundamental molecular parameter of copolymers. High‐temperature interactive liquid chromatography (HT‐HPLC) has recently emerged as a new analytical technique for determination of the CCD of semicrystalline copolymers of ethylene and polar comonomers. With the aim of comparing the results of HT‐HPLC with those from the traditionally used temperature rising elution fractionation (TREF) and crystallization analysis fractionation (CRYSTAF) techniques, three ethylene‐vinyl acetate (EVA) copolymers were fractionated by TREF and the fractions were analyzed by HT‐HPLC. HT‐HPLC‐Fourier transform‐infrared (FT‐IR) spectroscopy showed that individual fractions of different VA‐content coelute in the HPLC. While the separation in TREF and CRYSTAF is mainly the result of the overall effect of alkyl branches and VA‐comonomer units, in HT‐HPLC it is the polar comonomer that selectively contributes to the adsorption. Thus, HT‐HPLC leads to a much more detailed knowledge of the distribution of the structured units; in addition, it saves time.magnified image

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Section: Resultssupporting

confidence: 92%

Comparison of High‐Temperature HPLC, CRYSTAF and TREF for the Analysis of the Chemical Composition Distribution of Ethylene‐Vinyl Acetate Copolymers

Albrecht

Brüll²,

Macko

et al. 2009

Macro Chemistry & Physics

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“…To find the critical conditions for a specific polymer, numerous isocratic experiments with samples of different molar masses must be performed. Aiming at decreasing the number of experiments needed to identify the exact critical compositions, one can use a method to predict critical conditions by using a few linear gradient experiments as described by Bashir et al [17]. They suggested that the eluent composition at elution for a high molar mass sample is close to the critical composition for that specific polymer.…”

Section: Resultsmentioning

confidence: 99%

Development of Fast Gradient Separations for Different Polymethacrylates

Brüll¹,

Pasch

Bashir³

2006

E-Polymers

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Liquid chromatography of polymers is traditionally a slow technique with analysis times of typically 30 min per sample. To adapt liquid chromatographic techniques to combinatorial materials research the sample throughput must be significantly increased. Preferably, the analysis time per sample is to be reduced to a few minutes. Short analysis times can be achieved using high resolution stationary phases, high flow rates, and fast gradients. The present work demonstrates that gradient HPLC of polymethacrylates can be accomplished in less than 2 min. The fast separation of poly(methyl methacrylate), poly(i-propyl methacrylate), poly(n-butyl methacrylate), poly(tbutyl methacrylate), and poly(n-decyl methacrylate) is conducted on a short monolithic stationary phase using a flow rate of up to 7 mL/min. The optimization of the gradient is conducted by running a number of linear gradients and by simulating an optimum step gradient. Further modification of the simulated gradient results in the desired short analysis times.

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“…Time, material, and labor saving is meaningful but it is advised to check the actual critical conditions employing the conventional plot V R versus log M with the eluent composition identified by means of the Cools' method. Bashir et al [45] proposed to employ eluent gradient LC for estimation of critical eluent composition. Macko and Hunkeler [46] collected literature data on critical eluent compositions for numerous polymer column packing/temperature systems.…”

Section: Demanding Identification Of Critical Conditionsmentioning

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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Fast determination of critical eluent composition for polymers by gradient chromatography

Cited by 48 publications

References 19 publications

Comparison of High‐Temperature HPLC, CRYSTAF and TREF for the Analysis of the Chemical Composition Distribution of Ethylene‐Vinyl Acetate Copolymers

Comparison of High‐Temperature HPLC, CRYSTAF and TREF for the Analysis of the Chemical Composition Distribution of Ethylene‐Vinyl Acetate Copolymers

Development of Fast Gradient Separations for Different Polymethacrylates

Critical assessment of “critical” liquid chromatography of block copolymers

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