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Chemical Pathways for Galactoglucomannan-based Materials
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Polysaccharides are an important resource for a variety of products, from food via fuel supply to functional materials of every kind. Due to their natural diversity they can be found in many special applications, e.g. in the biomedical sector and are the major renewable resource for materials of many kinds.

Recently, a fairly unused group of polysaccharides, so called

hemicelluloses, have attracted increasing attention due to their high availability and promising properties in combination with renewability and a potentially low price.

This thesis presents pathways for the chemical modification of the water-soluble hemicellulose

acetylated galactoglucomannan (AcGGM), enabling this raw material to be utilized in the synthetic design of new classes of materials.

Based on the chemical modification of the hydroxyl groups with crosslinkable groups in combination with the naturally high hydrophilicity, synthetic pathways for the production of functional hydrogels are presented. Thanks to the great availability and the native properties of AcGGM, this material was found to be an outstanding candidate in this respect and was adjudged to be a cheap and green resource for hydrogel design.

For this purpose, a three-step method was devised consisting of (1) the carbonyldiimidazole activation of primary hydroxylated vinylic compounds, (2) the substitution of hydroxyl groups of the AcGGM backbone with vinylic functions, and (3) radical crosslinking yielding a hydrophilic three-dimensional network – a hydrogel.

Crosslinking strategies were varied from photo-crosslinking in dimethyl sulfoxide (DMSO) to redox-initiated crosslinking in H

2O, with the objective of adapting the synthesis to benign conditions. Varying the crosslinking species as well as the medium was found to have a significant influence on the resulting gels’ properties, such as swelling capacity and G-modulus. Swelling capacity could be varied between ~0.6 and ~23 times the gel’s own weight and the G-modulus ranged from 0.4 to 145 kPa.

AcGGM and 2-hydroxy ethyl methacrylate (HEMA) gels were studied further and evaluated for their suitability as drug delivery systems for two model drugs (caffeine and Vitasyn Blue) varying size, polarity, and hydrophilicity of the drug to be II

released. It was found that the gels composition as well as a second modification with maleic acid anhydride affects the release properties.

Taking well-studied polysaccharide modification chemistry one step further and combining it with state of the art polymer synthesis, graft-copolymers of AcGGM were successfully synthesized via single-electron-transfer living-radical polymerization (SET-LRP). For this purpose, a macroinitiator was derived from AcGGM to enable a grafting of diverse hydrophilic and hydrophobic monomers from the AcGGM under benign conditions. Hybrid materials of the natural polymer AcGGM as a backbone with synthetic poly(methyl acrylate), poly(methyl methacrylate), poly(acrylamide), and poly(N-isopropyl acrylamide) graft-copolymers with a brush-like architecture were successfully synthesized, yielding molecular weights of up to 240∙10³ g ∙ mol

-1. As expected, the solubility and thermal properties were significantly altered, opening a wider range of potential applications.

We conclude that the presented chemical pathways are important steps towards a promising future for hemicelluloses as raw materials and their derivatives as shown for the resource AcGGM.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , viii, 76 p.
Series
Trita-CHE-Report, ISSN 1654-1081
Keyword [en]
Polysaccharides, hemicelluloses, galactoglucomannan, renewable, chemical modification, hydrogels, swelling, crosslinking, release, SET-LRP, living polymerization, grafting, hybrid materials
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-34007ISBN: 978-91-7415-989-9 (print)OAI: oai:DiVA.org:kth-34007DiVA: diva2:418535
Public defence
2011-06-14, F3, Lindstedtsvägen 26, KTH, Stockholm, 09:00 (English)
Opponent
Supervisors
Note
QC 20110530Available from: 2011-05-30 Created: 2011-05-23 Last updated: 2011-05-30Bibliographically approved
List of papers
1. Drug Diffusion in Neutral and Ionic Hydrogels Assembled from Acetylated Galactoglucomannan
Open this publication in new window or tab >>Drug Diffusion in Neutral and Ionic Hydrogels Assembled from Acetylated Galactoglucomannan
Show others...
2009 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 112, no 4, 2401-2412 p.Article in journal (Refereed) Published
Abstract [en]

In this study, hydrogels based on acetylated galactoglucomannan (AcGGM)-a hemicellulose present in softwood-were synthesized and examined for their properties in drug-release systems using two model Substances of different molecular weight, size, and polarity (caffeine and vitasyn blue). Neutral hydrogels were produced from functionalized AcGGM using hydroxyethyl methacrylate (HEMA) coupled via carbonyldiimidazole (CDI) and a co-monomer in a radical-initiated polymerization. Through a second modification reaction between the HEMA-modified AcGGM (M-AcGGM-methacrylated AcGGM) and maleic anhydride, a "double-modified" AcGGM (CM-AcGGM-carboxylated M-AcGGM) was successfuly, formed that could be cross-linked to form ionic hydrogels by the very same polymerization method. The neutral hydrogels showed drug release kinetics that could be easily regulated by changing the relative amount of the methacrylated AcGGM and its corresponding degree of methacrylation. The drug release rate and the Fickian swelling cl creased with an increase in these two aforementioned parameters. The ionic hydrogels showed quicker release kinetics and higher swelling capabilities than the corresponding nonionic gels did, especially at neutral conditions. Under acidic conditions, the release speed was lowered as expected because of protonation of carboxylic functionalities. Based on the findings we conclude that these novel hemicellulose-containing hydrogels have future prospects in drug release formulations, e.g., in a later stage of development for application in oral drug administration technology.

Keyword
hemicellulose, hydrogels, renewable resources, release, cross-linking, hemicellulose-based hydrogels, spruce picea-abies, renewable sources, biodegradable polymers, l. karst, wood, films, water
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-18275 (URN)10.1002/app.29878 (DOI)000264449500065 ()2-s2.0-64249084593 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Alkenyl-Functionalized Precursors for Renewable Hydrogels Design
Open this publication in new window or tab >>Alkenyl-Functionalized Precursors for Renewable Hydrogels Design
2009 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 47, no 14, 3595-3606 p.Article in journal (Refereed) Published
Abstract [en]

A library of crosslinking chemistries for the hydrogel synthesis based on the hemicellulose acetylated galactoglucomannan (AcGGM) has been developed, demonstrated, and evaluated. A three-step route was elaborated including (1) the carbonyldiimidazole activation of primary hydroxylated vinylic molecules such as acrylates, vinyl alcohols, and vinyl ethers, (2) the covalent coupling of the alkenyl precursors to the polysaccharide backbone hydroxyls, and (3) the radical crosslinking of pendant vinyl functionalities affording a hydrophilic network. Crosslinking strategies explored include redox initiation and photo initiation, with an effort to adapt the suggested synthesis routes to benign conditions. The different functionalization strategies were shown to influence the resulting gel's properties. Varying the crosslinking media was found to be a strong tool to tune the properties of the gels. Modifications were in all cases verified by means of NMR and FTIR, and the gels were characterized with respect to swelling capacity and rheological parameters. It was shown that by adjusting the synthesis parameters, the resulting properties of the AcGGM gels could be custom-made for a given performance.

Keyword
crosslinking, galactoglucomannan, hemicellulose, hydrogels, polysaccharides, swelling, hemicellulose-based hydrogels, biodegradable polymers, delivery, softwood, water
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-18552 (URN)10.1002/pola.23444 (DOI)000267444200011 ()2-s2.0-67650669939 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Hemicellulose-Based Multifunctional Macroinitiator for Single-Electron-Transfer Mediated Living Radical Polymerization
Open this publication in new window or tab >>Hemicellulose-Based Multifunctional Macroinitiator for Single-Electron-Transfer Mediated Living Radical Polymerization
2011 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 1, 253-259 p.Article in journal (Refereed) Published
Abstract [en]

A multifunctional macroinitiator for single-electron-transfer mediated living radical polymerization (SET-LRP) was designed from acetylated galactoglucomannan (AcGGM) by alpha-bromoisobutyric acid functionalization of the anomeric hydroxyl groups on the heteropolysaccharide backbone. This macroinitiator, with a degree of substitution of 0.15, was used in the SET-LRP of methyl acrylate, catalyzed by Cu-0/Me-6-TREN in DMSO, DMF, or DMSO/H2O in various, concentrations. Kinetic analyses confirm high conversions of up to 99.98% and a living behavior of the SET-LRP process providing high molecular weight hemicelluloses/methyl acrylate hybrid copolymers with a brush-like architecture.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-30565 (URN)10.1021/bm101357k (DOI)000285956700034 ()2-s2.0-78651329262 (Scopus ID)
Funder
Formas, 243-2008-129
Note
QC 20110301Available from: 2011-03-01 Created: 2011-02-28 Last updated: 2017-12-11Bibliographically approved
4. A versatile single-electron-transfer mediated living radical polymerization route to galactoglucomannan graft-copolymers with tunable hydrophilicity
Open this publication in new window or tab >>A versatile single-electron-transfer mediated living radical polymerization route to galactoglucomannan graft-copolymers with tunable hydrophilicity
2011 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 49, no 11, 2366-2372 p.Article in journal (Refereed) Published
Abstract [en]

Cu(0) mediated living radical polymerization was successfully applied to synthesize graft-copolymers from the hemicellulose acetylated galactoglucomannan. Functionalizing the polysaccharide backbone with α-bromo isobutyric acid gave rise to a macroinitiator for single-electron-transfer mediated living radical polymerization (SET-LRP). This macroinitiator with a degree of substitution of 0.15 or 0.20 was used in the graft-SET-LRP of methyl methacrylate in dimethyl sulfoxide as well as N-isopropyl acrylamide and acrylamide in water. Kinetic analyses confirm conversions of up to 73% and a controlled behavior of the SET-LRP process providing high molecular weight hemicellulose-based hybrid copolymers with a brush-like architecture. Derived graft-copolymers varied significantly in solubility properties, ranging from hydrophobic via temperature responsive water-solubility to water-soluble.

Keyword
Acrylamides; Controlled behavior; Degree of substitution; Galactoglucomannan; hemicellulose; High molecular weight; Hybrid copolymer; hydrophilic polymers; Isobutyric acid; Kinetic analysis; Living radical polymerization; Macroinitiators; Methyl methacrylates; N-isopropylacrylamides; Renewable resource; SET-LRP; Single electron; Solubility properties; Temperature-responsive; Water solubilities, Acrylic monomers; Amides; Atom transfer radical polymerization; Cellulose; Copolymerization; Copolymers; Dimethyl sulfoxide; Esters; Functional polymers; Grafting (chemical); Hydrogels; Hydrophilicity; Single electron transistors; Solubility; Transients; Water resources, Polymers
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-34259 (URN)10.1002/pola.24666 (DOI)000290759400006 ()2-s2.0-79955371392 (Scopus ID)
Note
QC 20110530Available from: 2011-05-30 Created: 2011-05-30 Last updated: 2017-12-11Bibliographically approved

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