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Porous polymeric materials for chromatography: Synthesis, functionalization and characterization
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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 [en]
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: urn:nbn:se:umu:diva-30314ISBN: 978-91-7264-934-7 (print)OAI: oai:DiVA.org:umu-30314DiVA: diva2:281573
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
List of papers
1. A study of surface modification and anchoring techniques used in the preparation of monolithic microcolumns in fused silica capillaries.
Open this publication in new window or tab >>A study of surface modification and anchoring techniques used in the preparation of monolithic microcolumns in fused silica capillaries.
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2006 (English)In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 29, no 1, 14-24 p.Article in journal (Refereed) Published
Abstract [en]

Based on a survey of the literature on pretreatment of fused silica capillaries, 3 etching procedures and 11 silanization protocols based on the vinylic silane 3-((trimethoxysilyl)propyl) methacrylate (gamma-MAPS) were found to be most representative as a means of ensuring attachment of in situ prepared vinylic polymers. These techniques were applied to fused silica capillaries and the success in establishing the intended surface modification was assessed. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical state of the surface, providing information regarding presence of the reagent bound to the capillary. Wetting angles were measured and correlated with the XPS results. An adherence test was done by photopolymerization of a 2 mm long plug of 1,6-butanediol dimethacrylate in the prepared capillaries and evaluation of its ability to withstand applied hydraulic pressure. SEM was also performed in cases where the plug was released or other irregularities were observed. Finally, the roughness of the etched surface, considered to be of importance, was assessed by atomic force microscopy. Alkaline etching at elevated temperature provided a surface roughness promoting adhesion. The commonly used silanization protocols involving water in the silanization or washing steps gave inadequate surface treatment. The best silanization procedure was based on toluene as a solvent.

Place, publisher, year, edition, pages
Wiley, 2006
Keyword
Capillary columns, Fused silica capillary, Monoliths, Surface modification
Identifiers
urn:nbn:se:umu:diva-11145 (URN)10.1002/jssc.200500294 (DOI)16485705 (PubMedID)
Available from: 2008-03-27 Created: 2008-03-27 Last updated: 2015-09-28Bibliographically approved
2. Novel monolithic materials using poly(ethylene glycol) as porogen for protein separation
Open this publication in new window or tab >>Novel monolithic materials using poly(ethylene glycol) as porogen for protein separation
2006 (English)In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 47, no 8, 2603-2611 p.Article in journal (Refereed) Published
Abstract [en]

Several recipes are described for the preparation of porous polymeric monoliths in the capillary format, using poly(ethylene glycol) (PEG) as porogen as well as constituent in the monomer mixture. Acrylic or methacrylic monomers with a variety of terminal groups, with and without ethylene glycol links of differing lengths in the side chains, have been used in combination with triethylene glycol dimethacrylate (TEGDMA) and trimethylol-propane trimethacrylate (TRIM) as cross-linkers. PEGs of 4–20 kDa molecular weight dissolved in 2-methoxy-ethanol were used as porogens to yield large, biocompatible pores. A number of common solvents have been used as co-porogens for the PEGs, and the surface areas, median pore diameters, and back pressures of the resulting monoliths have been correlated with a number of molecular descriptors by means of chemometrics to describe the results. Photopolymerizations induced by either continuous or pulsed UV light were furthermore compared. Pore size distribution and surface area characterization have been assessed by nitrogen adsorption–desorption and mercury intrusion porosimetry, and scanning electron microscopy (SEM) was used to evaluate the differences in macroporous morphology obtained with the different porogen solutions. Mixtures selected from screening syntheses carried out in vials have been implemented in 100 μm fused silica capillaries and the back pressures measured and cross-validated with the pore information. Some of these capillary columns were finally tested for the separation of proteins using micro-HPLC.

Place, publisher, year, edition, pages
Guildford, Surrey: Butterworth, 2006
Keyword
Monolith capillary columns for liquid chromatography, Poly(ethylene glycol), Protein separation
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-5523 (URN)10.1016/j.polymer.2006.01.096 (DOI)
Available from: 2006-11-10 Created: 2006-11-10 Last updated: 2017-05-18Bibliographically approved
3. Gradient polymer elution chromatography of methacrylate Telomers on monolithic capillary columns prepared by nitroxide-mediated polymerization
Open this publication in new window or tab >>Gradient polymer elution chromatography of methacrylate Telomers on monolithic capillary columns prepared by nitroxide-mediated polymerization
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Linear methacrylate telomers prepared by isopropylxanthic disulfide photoiniferted polymerization of 2-hydroxyethyl methacrylate, methyl methacrylate, and ethyl methacrylate have been separated from their precursor monomers using gradient polymer elution chromatography (GPEC) on a monolithic capillary column. The capillary monoliths were prepared by thermally initiated radical polymerization of styrene and divinylbenzene controlled by 1-carboxy-PROXYL stable free radicals, and characterized by nitrogen adsorption and mercury intrusion porosimetry. The separations in GPEC mode were performed using a mobile phase gradient from water to methanol, where water is the non-solvent and methanol the good solvent with respect to the telomers. Successful separation of telomers from their monomer was achieved for all tested telomers. In addition, it was observed that the retention times of the intact telomers were different from those of telechelic oligomers produced by hydrolysing the isopropylxanthic terminals. The current set-up is therefore promising both for monitoring of the progress of photoiniferted polymerizations and to monitor the hydrolysis of resulting polymerized oligomers into thiol-terminated telechelics.

Keyword
Gradient polymer elution chromatography, telechelics, living polymerization, monoliths, separation of polymers
National Category
Analytical Chemistry Polymer Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-30309 (URN)
Available from: 2009-12-16 Created: 2009-12-16 Last updated: 2017-05-18Bibliographically approved
4. Differences in porous characteristics of styrenic monoliths prepared by controlled thermal polymerization in molds of varying dimensions
Open this publication in new window or tab >>Differences in porous characteristics of styrenic monoliths prepared by controlled thermal polymerization in molds of varying dimensions
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
Keyword
HPLC, Miniaturization, Organic monolithic materials, Porous properties
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-30310 (URN)10.1002/jssc.200900668 (DOI)000274578000008 ()
Available from: 2009-12-16 Created: 2009-12-16 Last updated: 2012-02-22Bibliographically approved
5. Plasma brominated polymer particles as grafting substrate for thiol-terminated telomers
Open this publication in new window or tab >>Plasma brominated polymer particles as grafting substrate for thiol-terminated telomers
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2010 (English)In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 33, no 11, 1563-70 p.Article in journal (Refereed) Published
Abstract [en]

A combined surface activation and "grafting to" strategy was developed to convert divinylbenzene particles into weak cation exchangers suitable for protein separation. The initial activation step was based on plasma modification with bromoform, which rendered the particles amenable to further reaction with nucleophiles by introducing Br to a surface content of 11.2 atom-%, as determined by X-ray photoelectron spectroscopy. Grafting of thiol-terminated glydicyl methacrylate telomers to freshly plasma activated surfaces was accomplished without the use of added initiator, and the grafting was verified both by reduction in bromine content and the appearance of sulfur-carbon linkages, showing that the surface grafts were covalently bonded. Following grafting the attached glydicyl methacrylate telomer tentacles were further modified by a two-step procedure involving hydrolysis to 2,3-hydroxypropyl groups and conversion of hydroxyl groups to carboxylate functionality by succinic anhydride. The final material was capable of baseline separating four model proteins in 3 min by gradient cation exchange chromatography in a fully aqueous eluent.

Place, publisher, year, edition, pages
Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA, 2010
Keyword
Grafting to, Non-porous divinylbenzene particles, Plasma bromination, Precipitation polymerization, Telomer surface modification
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-34218 (URN)10.1002/jssc.201000028 (DOI)000278829700005 ()20432486 (PubMedID)
Available from: 2010-05-21 Created: 2010-05-21 Last updated: 2017-05-18Bibliographically approved

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