Multiple‐Injection Method in High‐Temperature Two‐Dimensional Liquid Chromatography (2D HT‐LC)

Mekap, Dibyaranjan; Macko, Tibor; Brüll, Robert; Cong, Rongjuan; deGroot, Willem; Parrott, Albert R.; Yau, Wallace W.

doi:10.1002/macp.201300649

Cited by 9 publications

(5 citation statements)

References 42 publications

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“…Then the Hypercarb column was loaded by flowing decanol at 0.5 mL/min through the column and using a loop of 300 μL. Multiple-injection method was used . 25 injections were made without eluting any polymer.…”

Section: Methodsmentioning

confidence: 99%

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NMR Study of the Separation Mechanism of Polyethylene–Octene Block Copolymer by HT-LC with Graphite

et al. 2015

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High temperature liquid chromatography (HT-LC) and temperature gradient interaction chromatography (TGIC) using a graphite substrate were recently invented to characterize polyolefin microstructures and composition distributions. Their separation mechanisms have been explored by using a series of random copolymers. In addition, the separation mechanism of TGIC for random copolymers was also studied with a high temperature NMR cryoprobe. The proposed separation mechanism for a random copolymer is that the separation is likely based on comonomer content, in other words, the number-averaged ethylene sequence length. Further understanding of HT-LC separation mechanism with polyethylene–octene block copolymers is beneficial in order to extend the use of HT-LC and TGIC to a wider variety of polyolefin materials, and to better characterize more challenging microstructures of new materials. With the high temperature NMR cryoprobe technology, it is possible to perform 13C NMR of polyolefins with a few milligrams of sample. This paper summarizes the NMR study of the materials obtained from preparative scale HT-LC on polyethylene–octene block copolymer with a high temperature NMR cryoprobe. The results show unambiguously that the HT-LC separation of polyethylene–octene block copolymer is mainly based on the interaction between hard block and the stationary phase, and the strength of the interaction is correlated to the total length of the hard block in the block copolymer.

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Section: Methodsmentioning

confidence: 99%

“…Multipleinjection method was used. 24 25 injections were made without eluting any polymer. After the column was loaded, the following pump program (Table 1) was used to elute the polymer for fraction collection.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

NMR Study of the Separation Mechanism of Polyethylene–Octene Block Copolymer by HT-LC with Graphite

et al. 2015

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“…Larger injection volume was desired for better signal intensity. It had been demonstrated that large injection volume did not overload the column . This is likely because the polymer samples were injected in decane, the solvent with weak elution strength.…”

Section: Methodsmentioning

confidence: 99%

Toward Absolute Chemical Composition Distribution Measurement of Polyolefins by High-Temperature Liquid Chromatography Hyphenated with Infrared Absorbance and Light Scattering Detectors

et al. 2014

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Chemical composition distribution (CCD) is a fundamental metric for representing molecular structures of copolymers in addition to molecular weight distribution (MWD). Solvent gradient interaction chromatography (SGIC) is commonly used to separate copolymers by chemical composition in order to obtain CCD. The separation of polymer in SGIC is, however, not only affected by chemical composition but also by molecular weight and architecture. The ability to measure composition and MW simultaneously after separation would be beneficial for understanding the impact of different factors and deriving true CCD. In this study, comprehensive two-dimensional chromatography (2D) was coupled with infrared absorbance (IR5) and light scattering (LS) detectors for characterization of ethylene-propylene copolymers. Polymers were first separated by SGIC as the first dimension chromatography (D1). The separated fractions were then characterized by the second dimension (D2) size exclusion chromatography (SEC) with IR5 and LS detectors. The concentrations and compositions of the separated fractions were measured online using the IR5 detector. The MWs of the fractions were measured by the ratio of LS to IR5 signals. A metric was derived from online concentration and composition data to represent CCD breadth. The metric was shown to be independent of separation gradients for an "absolute" measurement of CCD breadth. By combining online composition and MW data, the relationship of MW as a function of chemical composition was obtained. This relationship was qualitatively consistent with the results by SEC coupled to IR5, which measures chemical composition as a function of logMW. The simultaneous measurements of composition and MW give the opportunity to study the SGIC separation mechanism and derive chain architectural characteristics of polymer chains.

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“…[25][26][27][28][29][30][31][32][33] It has been shown that the adsorption strength of random ethylene/1-alkene copolymers is a function of concentration of the 1-alkene in the copolymers. The larger the concentration of the branches is, the smaller the adsorption of the copolymers.…”

Section: Introductionmentioning

confidence: 99%

“…Interactive HPLC systems, based on reversible adsorption and desorption of polyethylene on the surface of porous graphite at a temperature at which polyethylene stays in solution, were introduced into analytical laboratories starting from 2009 . It has been shown that the adsorption strength of random ethylene/1‐alkene copolymers is a function of concentration of the 1‐alkene in the copolymers.…”

Section: Introductionmentioning

confidence: 99%

High‐Temperature Solvent Gradient Liquid Chromatography of Model Long Chain Branched Polyethylenes

Macko

Brüll

Santonja-Blasco

et al. 2015

Macromolecular Symposia

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Summary:The high-temperature solvent gradient liquid chromatography system 1-decanol/1,2,4-trichlorobenzene/porous graphite Hypercarb TM has been applied to the separation of well-defined model long chain branched (LCB) polyethylenes with different architectures (star, H-type, super H-type, pompom, comb). The model LCB polyethylenes have been prepared by anionic polymerization of butadiene followed by click chemistry. After hydrogenation of the polybutadienes, the LCB samples contain $ 2 mol % ethyl branches randomly distributed along the backbone and the LCB, as is typical for linear low density polyethylene (LLDPE). The results indicate that the LCB does not influence the chromatographic separation substantially. The adsorption characteristics of the LCB copolymers are dominated by the SCB content. The presence of LCB increases the molar mass of the samples; however, the increase in molar mass from 100 kg/mol to 200 kg/mol does not influence chromatographic separations in the applied system of porous carbon and 1-decanol/ 1,2,4-trichlorobenzene.

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Multiple‐Injection Method in High‐Temperature Two‐Dimensional Liquid Chromatography (2D HT‐LC)

Cited by 9 publications

References 42 publications

NMR Study of the Separation Mechanism of Polyethylene–Octene Block Copolymer by HT-LC with Graphite

NMR Study of the Separation Mechanism of Polyethylene–Octene Block Copolymer by HT-LC with Graphite

Toward Absolute Chemical Composition Distribution Measurement of Polyolefins by High-Temperature Liquid Chromatography Hyphenated with Infrared Absorbance and Light Scattering Detectors

High‐Temperature Solvent Gradient Liquid Chromatography of Model Long Chain Branched Polyethylenes

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