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Porous Melamine-Formaldehyde Monoliths by Step-Growth Polymerization Reactions via an Organic Sol-gel Process
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Research Group for Reactive Polymers in Analytical Chemistry (RPAC))
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Research Group for Reactive Polymers in Analytical Chemistry (RPAC))
(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: urn:nbn:se:umu:diva-89309OAI: oai:DiVA.org:umu-89309DiVA: diva2:719786
Funder
Swedish Research Council, 2012-4000
Available from: 2014-05-27 Created: 2014-05-27 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Porous Polymeric Monoliths by Less Common Pathways: Preparation and Characterization
Open this publication in new window or tab >>Porous Polymeric Monoliths by Less Common Pathways: Preparation and Characterization
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
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:nbn:se:umu:diva-89322 (URN)978-91-7601-088-4 (ISBN)
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

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Elhaj, AhmedIrgum, Knut

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