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Differences in porous characteristics of styrenic monoliths prepared by controlled thermal polymerization in molds of varying dimensions
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Merck SeQuant AB, Umeå.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2010 (English)In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 33, no 2, 191-199 p.Article in journal (Refereed) Published
Abstract [en]

Nitroxide-mediated polymerization was used as a model system for preparing styrenic monolithic materials with significant mesopore contents in different mold formats, with the aim of assessing the validity of pore characterization of capillary monoliths by analysis of parallel bulk polymerized precursor solution. Capillary monoliths were prepared in 250 mm id fused silica tubes (quadruplicate samples, in total 17 m), and the batch polymerizations were carried out in parallel in 100 mL microvials and regular 2mL glass vials, both in quintuplicate. The monoliths recovered from the molds were characterized for their meso- and macroporous properties by nitrogen sorptiometry (three repeated runs on each sample), followed by a single analysis by mercury intrusion porosimetry. A total of 14 monolith samples were thus analyzed. A Grubbs’ test identified one regular vial sample as an outlier in the sorptiometric surface area measurements, and data from this sample were consequently excluded from the pore size calculations, which are based on the same nitrogen sorption data, and also from the mercury intrusion data set. The remaining data were subjected to single factor analyses of variance analyses to test if the porous properties of the capillary monoliths were different from those of the bulk monoliths prepared in parallel. Significant differences were found between all three formats both in their meso and macroporous properties. When the dimension was shrunk from conventional vial to capillary size, the specific surface area decreased from 52.274.7 to 34.671.7m2/g. This decrease in specific surface area was accompanied by a significant shift in median diameter of the through-pores, from 31073.9 to 544713 nm. None of these differences was obvious from the scanning electron micrographs that were acquired for each sample type. The common practice of determining the mesopore characteristics from analysis of samples prepared by parallel bulk polymerization and looking for changes in the macropore structure by visual assessment of SEMs are therefore both rather questionable, at least for monoliths of the kind used in this study.

Place, publisher, year, edition, pages
Wiley , 2010. Vol. 33, no 2, 191-199 p.
Keyword [en]
HPLC, Miniaturization, Organic monolithic materials, Porous properties
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-30310DOI: 10.1002/jssc.200900668ISI: 000274578000008OAI: oai:DiVA.org:umu-30310DiVA: diva2:281518
Available from: 2009-12-16 Created: 2009-12-16 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Porous polymeric materials for chromatography: Synthesis, functionalization and characterization
Open this publication in new window or tab >>Porous polymeric materials for chromatography: Synthesis, functionalization and characterization
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Separation science is heavily reliant on materials to fulfill ever more complicated demands raised by other areas of science, notably the rapidly expanding molecular biosciences and environmental monitoring. The key to successful separations lies in a combination of physical properties and surface chemistry of stationary phases used in liquid chromatographic separation, and this thesis address both aspects of novel separation materials.

Methods: The thesis accounts for several approaches taken during the course of my graduate studies, and the main approaches have been i) to test a wild-grown variety of published methods for surface treatment of fused silica capillaries, to ascertain firm attachment of polymeric monoliths to the wall of microcolumns prepared in silica conduits; ii) developing a novel porogen scheme for organic monoliths including polymeric porogens and macromonomers; iii) evaluating a mesoporous styrenic monolith for characterization of telomers intended for use in surface modification schemes and; iv) to critically assess the validity of a common shortcut used for estimating the porosity of monoliths prepared in microconduits; and finally v) employing plasma chemistry for activating and subsequently modifying the surface of rigid, monodisperse particles prepared from divinylbenzene.

Results: The efforts accounted for above have resulted in i) better knowledge of the etching and functionalization parameters that determine attachment of organic monoliths prepared by radical polymerization to the surface of silica; ii) polar methacrylic monoliths with a designed macroporosity that approaches the desired "connected rod" macropore morphology; iii) estab¬lishing the usefulness of monoliths prepared via nitroxide mediated polymerization in gradient polymer elution chromatography; iv) proving that scanning electron microscopy images are of limited value for assessing the macroporous properties of organic monoliths, and that pore measurements on externally polymerized monolith cocktails do not represent the porous properties of the same cocktail polymerized in narrow confinements; and v) showing that plasma bromination can be used as an activation step for rigid divinylbenzene particles to act as grafting handles for epoxy-containing telomers, that can be attached in a sufficiently dense layer and converted into carboxylate cation exchange layer that allows protein separations in fully aqueous eluents.

Place, publisher, year, edition, pages
Umeå: Kemiska Institutionen, Umeå universitet, 2009. 45 p.
Keyword
porous polymer monolith, pore size distribution, nitrogen sorptiometry, mercury intrusion porosimetry, scanning and transmission electron microscopy, plasma functionalization
National Category
Analytical Chemistry Analytical Chemistry Polymer Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-30314 (URN)978-91-7264-934-7 (ISBN)
Public defence
2010-01-15, KBC-Huset, KB3A9, Umeå Universitet, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2009-12-18 Created: 2009-12-16 Last updated: 2017-05-18Bibliographically approved

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