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Introduction
The origin of unfavorable peak dispersion characteristics for small-molecule separations utilizing polymer-monolithic materials is not yet understood and severely limits the application possibilities of these columns. Detailed insights in the micro- and mesopores structure of polymer monolithic stationary phase materials can ultimately lead to a better understanding of the relation between the monolithic column structure and peak dispersion in high-performance liquid chromatography.
Methods
Two different poly(styrene-co-divinylbenzene) monolithic materials were synthesized via a thermally-initiated free-radical polymerization. The ratio of THF/1-decanol was varied to yield different morphologies. These monolithic materials were synthesized in parallel in-situ in silanized 200 µm I.D. capillary tubing and in bulk quantity (2 mL vials). Complementary techniques, gas adsorption (applying non-local density function theory (NLDFT)), mercury-intrusion porosimetry, and scanning-electron and atomic-force microscopy, have been applied to characterize the pore-size distributions of the monolithic materials on the micro-, meso- and macroscopic level.
Results
Increasing the ratio of THF/1-decanol in the polymerization mixture by 5% resulted in a decrease in average globule size from 400 nm to 150 nm. Mercury-intrusion porosimetry data shows a reduction of macropore size from 2000 nm to 200 nm. Gas-adsorption data fitted with NLDFT models reveals the presence of trimodal mesopore-size distributions (with mode pore diameters at 4 nm, 16 nm, and 24 nm). The material with a small domain size yields substantially higher adsorption isotherms compared to the sample with larger feature sizes and a sixfold higher pore-volume was noted for the monolith with small domain size. This higher pore volume could be explained by the difference in surface area to material volume. If argon can only penetrate the outer layer of the globules, a large portion of (probably microporous) material inside large globules remains shielded off, hence not contributing to porosity within the studied range. A hysteresis between adsorption and desorption was noted over a very broad range of relative pressures. This is likely to be caused by the dissolving of argon into the polymer, which is only again released at very low pressures.
Novel aspects: Argon adsorption data processed via density function theory provides reliable info on micro- and mesoscopic nature of polymer monoliths.
The origin of unfavorable peak dispersion characteristics for small-molecule separations utilizing polymer-monolithic materials is not yet understood and severely limits the application possibilities of these columns. Detailed insights in the micro- and mesopores structure of polymer monolithic stationary phase materials can ultimately lead to a better understanding of the relation between the monolithic column structure and peak dispersion in high-performance liquid chromatography.
Methods
Two different poly(styrene-co-divinylbenzene) monolithic materials were synthesized via a thermally-initiated free-radical polymerization. The ratio of THF/1-decanol was varied to yield different morphologies. These monolithic materials were synthesized in parallel in-situ in silanized 200 µm I.D. capillary tubing and in bulk quantity (2 mL vials). Complementary techniques, gas adsorption (applying non-local density function theory (NLDFT)), mercury-intrusion porosimetry, and scanning-electron and atomic-force microscopy, have been applied to characterize the pore-size distributions of the monolithic materials on the micro-, meso- and macroscopic level.
Results
Increasing the ratio of THF/1-decanol in the polymerization mixture by 5% resulted in a decrease in average globule size from 400 nm to 150 nm. Mercury-intrusion porosimetry data shows a reduction of macropore size from 2000 nm to 200 nm. Gas-adsorption data fitted with NLDFT models reveals the presence of trimodal mesopore-size distributions (with mode pore diameters at 4 nm, 16 nm, and 24 nm). The material with a small domain size yields substantially higher adsorption isotherms compared to the sample with larger feature sizes and a sixfold higher pore-volume was noted for the monolith with small domain size. This higher pore volume could be explained by the difference in surface area to material volume. If argon can only penetrate the outer layer of the globules, a large portion of (probably microporous) material inside large globules remains shielded off, hence not contributing to porosity within the studied range. A hysteresis between adsorption and desorption was noted over a very broad range of relative pressures. This is likely to be caused by the dissolving of argon into the polymer, which is only again released at very low pressures.
Novel aspects: Argon adsorption data processed via density function theory provides reliable info on micro- and mesoscopic nature of polymer monoliths.
Originele taal-2 | English |
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Status | Published - 24 jun 2015 |
Evenement | HPLC 2015 - Geneva, Switzerland Duur: 21 jun 2015 → 25 jun 2015 |
Conference
Conference | HPLC 2015 |
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Land/Regio | Switzerland |
Stad | Geneva |
Periode | 21/06/15 → 25/06/15 |
Vingerafdruk
Duik in de onderzoeksthema's van 'Poster: A comprehensive study of the macro- and mesopores size distributions of polymer monoliths using complementary physical characterization techniques'. Samen vormen ze een unieke vingerafdruk.Projecten
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SRP6: SRP (Zwaartepunt): exploitatie van de voordelen van de Orde in Opsluiting voor een groenere chemie
Desmet, G., Denayer, J., Denayer, J., Desmet, G. & Denayer, J.
1/11/12 → 31/10/22
Project: Fundamenteel