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Porous Polymeric Monoliths by Less Common Pathways: Preparation and Characterization
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Reactive Polymers for Analytical Chemistry (RPAC))
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on my endeavors to prepare new porous polymeric monoliths that are viable to use as supports in flow-through processes. Polymer monoliths of various porous properties and different chemical properties have been prepared utilizing the thermally induced phase separation (TIPS) phenomenon and step-growth polymerization reactions. The aim has been to find appropriate synthesis routes to produce separation supports with fully controlled chemical, physical and surface properties. This thesis includes preparation of porous monolithic materials from several non-cross-linked commodity polymers and engineering plastics by dissolution/precipitation process (i.e. TIPS). Elevated temperatures, above the upper critical solution temperature (UCST), were used to dissolve the polymers in appropriate solvents that only dissolve the polymers above this critical temperature. After dissolution, the homogeneous and clear polymer-solvent solution is thermally quenched by cooling. A porous material, of three dimensional structure, is then obtained as the temperature crosses the UCST. More than 20 organic solvents were tested to find the most compatible one that can dissolve the polymer above the UCST and precipitate it back when the temperature is lowered. The effect of using a mixture of two solvents or additives (co-porogenic polymer or surfactant) in the polymer dissolution/precipitation process have been studied more in depth for poly(vinylidine difluoride) (PVDF) polymers of two different molecular weight grades. Monolithic materials showing different pore characteristics could be obtained by varying the composition of the PVDF-solvent mixture during the dissolute­ion/precipitation process. Step-growth polymerization (often called polycondensat­ion reaction) combined with sol-gel process with the aid of porogenic polymer and block copolymer surfactant have also been used as a new route of synthesis for production of porous melamine-formaldehyde (MF) monoliths. In general, the meso- and macro-porous support materials, for which the synthesis/preparation is discussed in this thesis, are useful to a wide variety of applications in separation science and heterogeneous reactions (catalysis).

Place, publisher, year, edition, pages
Umeå: Umeå university , 2014. , 63 p.
Keyword [en]
Monolith, commodity polymer, thermally induced phase separation, dissolution-precipitation, polymer solvents, porogenic polymer, step-growth polymerization, separation science, melamine-formaldehyde
National Category
Analytical Chemistry Polymer Chemistry Materials Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-89322ISBN: 978-91-7601-088-4 (print)OAI: oai:DiVA.org:umu-89322DiVA: diva2:719902
Public defence
2014-06-13, KB3B1, KBC-huset, Umeå universitet, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2014-05-28 Created: 2014-05-27 Last updated: 2014-05-28Bibliographically approved
List of papers
1. Monolithic space-filling porous materials from engineering plastics by thermally induced phase separation
Open this publication in new window or tab >>Monolithic space-filling porous materials from engineering plastics by thermally induced phase separation
2014 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 18, 15653-15666 p.Article in journal (Refereed) Published
Abstract [en]

Six different uncompounded engineering and commodity polymers were evaluated for their ability to produce space-filling monolithic entities by thermally induced phase separation (TIPS) from 22 different solvents. Attempts were first made to dissolve the polymers at elevated temperatures, selected below the boiling point of each solvent. Then the solutions of polymers that were homogeneous dissolved underwent a controlled temperature decrease to induce a phase separation as the upper critical solution temperature was passed. Twelve of the solvents gave monolithic entities by this procedure, materials that were characterized with regard to their specific surface area and pore size distribution. These measured parameters were then correlated with their macroporous morphology, assessed by scanning electron microscopy. Monolithic materials with widely different mesoporous properties were obtained with specific surface areas ranging from 169 m(2)/g to structures with essentially nonporous skeletons and distinct mesopore size distribution modes from 6 to 15 nm. The materials furthermore had a wide variation in their macroporous morphologies-among the same polymer processed in different solvents and between different polymers dissolved in the same solvent. TIPS processing therefore appears to be a viable route to prepare space-filling meso- and macroporous support materials for a wide variety of purposes in separation science and heterogeneous chemistry.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2014
Keyword
monolithic supports, polymeric scaffolds, heterogeneous chemistry, separation science, thermally induced phase separation
National Category
Chemical Sciences Nano Technology
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-89306 (URN)10.1021/am502977z (DOI)000342328300006 ()
Funder
Swedish Research Council, 2012-4000
Note

Included in thesis in manuscript form.

Available from: 2014-05-27 Created: 2014-05-27 Last updated: 2017-12-05Bibliographically approved
2. Porous Space-filling Monolithic Polyvinylidene Difluoride (PVDF) Materials by Thermally Induced Phase Separation
Open this publication in new window or tab >>Porous Space-filling Monolithic Polyvinylidene Difluoride (PVDF) Materials by Thermally Induced Phase Separation
(English)In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291Article in journal (Refereed) Submitted
Abstract [en]

Thermally induced phase separation was assessed as a means of producing space-filling monoliths from PVDF of three dif­ferent molecular weights in twenty-two different solvents spanning a wide polarity range. Monolithic materials were produced in six out of these solvents; n-butyl butyrate, 1,4-dimethoxy­benzene, cyclohexanone, 2,5-hexanedione, dimethyl succinate, and e-caprolact­one. These monoliths had specific surface areas up to 35 m2/g, with the majority of the measured sur­face area attributable to pores in the mesoporous region from 5-20 nm, depending on solvent. Scanning elec­tron microscopy images re­vealed radically different structures at the macropore level. In three of the samples essentially monodis­perse particles in the 4-5 µm diameter range were found and verified to be of the same chemical compo­sition as the monolithic part of the precipitate. These particles appeared for PVDF of different mole­cular weights and seem to have phase separated by a mechanism dif­fering from the bulk monolith, which could hint at a novel way to prepare monodisperse PVDF particles.

National Category
Chemical Sciences
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-89308 (URN)
Funder
Swedish Research Council, 2012-4000
Available from: 2014-05-27 Created: 2014-05-27 Last updated: 2017-12-05Bibliographically approved
3. Porous Melamine-Formaldehyde Monoliths by Step-Growth Polymerization Reactions via an Organic Sol-gel Process
Open this publication in new window or tab >>Porous Melamine-Formaldehyde Monoliths by Step-Growth Polymerization Reactions via an Organic Sol-gel Process
(English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093Article in journal (Refereed) Submitted
Abstract [en]

In this explorative study, twenty hydrophilic melamine-formaldehyde (MF) monolith materials were syn­the­sized by acid-catalyzed polycon­densation of systems consisting of an aqueous MF pre­condensate, a block copolymeric surfactant as main porogen, and short aliphatic polyethers as co-porogens, which were dispersed in three different organic solvents covering a wide span in polarity. The molecular size and type of aliphatic polyether (co-porogen), and of the ratio of solvents to the other components were investigated by an experimental design that resulted in monolithic materials covering a wide range of different meso- and macroporous properties. A multivariate assessment revealed that the strongest contributors to the mesopore size and the inversely related surface area were the co-porogens, whereas the macropore dimension was explained by the solvents and the ratio between solvents and the other components. Surface elemental analysis by XPS showed slight differen­ces in the bridging type between monoliths of opaque glass-like vs. white solid appearance. Measurements ζ-potentials in 10 mM ammonium acetate showed that the MF monoliths had no net charge at neutral pH, and +11 and –13 mV at pH 4 and 9.5, respectively.

National Category
Chemical Sciences
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-89309 (URN)
Funder
Swedish Research Council, 2012-4000
Available from: 2014-05-27 Created: 2014-05-27 Last updated: 2017-12-05Bibliographically approved
4. Porous Polyvinylidene Difluoride (PVDF) Monoliths via Thermally Induced Dissolution/Precipitation. Three Strategies to Pore-Tuning: Probing the possibilities of further controlling of the PVDF monolith pore formation process
Open this publication in new window or tab >>Porous Polyvinylidene Difluoride (PVDF) Monoliths via Thermally Induced Dissolution/Precipitation. Three Strategies to Pore-Tuning: Probing the possibilities of further controlling of the PVDF monolith pore formation process
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The porous properties and morphologies of the PVDF monoliths prepared via thermally induced dissolution/precipitation process were proved to be adjustable, by employing several porogenic additives to the PVDF/n-butyl butyrate matrix. PVDF monoliths have been separately precipitated from; only the main diluent (n-butyl butyrate); mixtures of the main diluent and a co-diluent; binary polymer mixtures (including an additional porogenic polymer such as poly ethylene glycol PEG200, PEG400 and poly propylene glycol PPG425); and the main diluent in the presence of a fluoro-surfactant (FSO, FSN). Their meso- and macro-porous properties were characterized by nitrogen cryoption measurements (3-5 repeated runs per sample), and a subsequent single analysis by mercury intrusion porosimetry. The visual assessment of the monoliths morphology differences were carried out using scanning electron microscopy (SEM).

National Category
Chemical Sciences
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-89313 (URN)
Available from: 2014-05-27 Created: 2014-05-27 Last updated: 2014-05-28Bibliographically approved

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