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Novel Possibilities for Advanced Molecular Structure Design for Polymers and Networks
KTH, Superseded Departments, Polymer Technology.ORCID iD: 0000-0002-1922-128X
2003 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Synthetic and degradable polymers are an attractive choicein many areas, since it is possible to control the way in whichthey are manufactured; more specifically, pathways tomanipulate the architecture, the mechanical properties and thedegradation times have been identified. In this work,L-lactide, 1,5-dioxepan-2-one and ε-caprolactone were usedas monomers to synthesize polymers with different architecturesby ring-opening polymerization. By using novel initiators,triblock copolymers, functionalized linear macromonomers andstar-shaped aliphatic polyesters with well-defined structureshave been synthesized. To synthesize triblock copolymers,cyclic germanium initiators were studied. The polymerizationproceeded in a controlled manner although the reaction rateswere low. To introduce functionality into the polymer backbone,functionalized cyclic tin alkoxides were prepared and used asinitiators. During the insertion-coordination polymerization,the initiator fragment consisting mainly of a double bond wasincorporated into the polymer backbone. The double bond wasalso successfully epoxidized and this gave unique possibilitiesof synthesizing graft polymers with precise spacing. Themacromonomer technique is a very effective method for producingwell-defined graft polymers. Spirocyclic tin initiators weresynthesized and used to construct star-shaped polymers. Thestar-shaped polymers were subsequently crosslinked in apolycondensation reaction. These crosslinked structures swelledin water, and swelling tests showed that by changing thestructure of the hydrogel network, the degree of swelling canbe altered. A first evaluation of the surface characteristicsof the linear triblock copolymers was also performed. AFManalysis of the heat-treated surfaces revealed nanometer-scalefibers and tests showed that keratinocytes were able to growand proliferate on these surfaces.

Place, publisher, year, edition, pages
Stockholm: KTH , 2003. , 78 p.
Keyword [en]
ring-opening polymerization, coordination-insertion, germanium, cyclic tin alkoxides, spirocyclic initiators, poly(L-lactide), poly(1, 5-dioxepan-2-one), triblock, star-shaped, network, functionalization, morphology, AFM
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-3623ISBN: 91-7283-577-X (print)OAI: oai:DiVA.org:kth-3623DiVA: diva2:9454
Public defence
2003-10-31, 00:00 (English)
Note
QC 20100602Available from: 2003-10-28 Created: 2003-10-28 Last updated: 2010-06-02Bibliographically approved
List of papers
1. Use of germanium initiators in ring-opening polymerization of L-lactide
Open this publication in new window or tab >>Use of germanium initiators in ring-opening polymerization of L-lactide
2003 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 41, no 19, 3074-3082 p.Article in journal (Refereed) Published
Abstract [en]

Three different, new germanium initiators were used for ring-opening polymerization Of L-lactide. Chlorobenzene and 120 degreesC was a usable polymerization system for solution polymerization, and the results from the polymerizations depended on the initiator structure and bulkiness around the insertion site. The average molecular weights as measured by size exclusion chromatography increased linearly with the monomer conversion, and the molecular weight dispersity was around 1.2 for initiators 1 and 2, whereas it was around 1.4 for initiator 3. The average molecular weight of poly(L-lactide) could be controlled with all three initiators by adding different ratios of monomer and initiator. The reaction rate for the solution polymerization was, however, overall extremely slow. With an initial monomer concentration of 1 M and a monomer-to-initiator ratio of 50, the conversion was 93% after 161 h for the fastest initiator. In bulk polymerization, 160 degreesC, the conversion was 90% after 10 h.

Keyword
germanium initiators, ring-opening polymerization, aliphatic polyesters, block copolymers, EPSILON-CAPROLACTONE, ALUMINUM ALKOXIDES, POLYLACTONES, 1, 5-DIOXEPAN-2-ONE, SALTS, LACTONES, LACTATE
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13185 (URN)10.1002/pola.10887 (DOI)000185172500016 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
2. L-lactide macromonomer synthesis initiated by new cyclic tin alkoxides functionalized for brushlike structures
Open this publication in new window or tab >>L-lactide macromonomer synthesis initiated by new cyclic tin alkoxides functionalized for brushlike structures
2001 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, no 21, 7281-7287 p.Article in journal (Refereed) Published
Abstract [en]

L-Lactide macromonomers with an incorporated double bond were successfully synthesized by controlled ring-opening polymerization initiated by two new cyclic tin alkoxides (1,1-di-n-butyl-stanna-2,7-dioxacyclo-4-heptene and 9,9,20,20-tetrabutyl-8,10,19,21-tetraoxa-9,20-distanna-dispiro[5.5.5.5]d ocosa-2,14-diene). Initiators and crude reaction mixtures were characterized by NMR. H-1 NMR analysis showed that the initiators were completely reacted in the polymerization and that both tin-oxygen bonds were reactive and participated in propagation. The polymerizations were performed in chloroform at 60 degreesC, and the molecular weight was effectively controlled by adjusting the monomer-to-initiator ratio. The molecular weight distribution was narrow (<1.1) for both high and low molecular weights (3000-72 000 g/mol). A plot of M-n vs conversion was linear up to a conversion of 98%, showing a system propagating in a controlled manner. The kinetic investigation showed that all of the polymerizations were first order in monomer and that no termination reactions occurred during polymerization.

Keyword
ring-opening polymerization, poly(l-lactide) macromonomers, macrocyclic polymerization, multiblock copolymers, aluminum alkoxides, graft-copolymers, polylactones, polyesters, pentaerythritol, caprolactone
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-13186 (URN)10.1021/ma0106898 (DOI)000171386300011 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
3. New functionalized polyesters to achieve controlled architectures
Open this publication in new window or tab >>New functionalized polyesters to achieve controlled architectures
2004 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 42, no 3, 444-452 p.Article in journal (Refereed) Published
Abstract [en]

Following our continued interest in the production of bioerodible and biodegradable functional polymers for biomedical applications, we synthesized and characterized new unsaturated polyesters. The presence of functional groups in the polymer backbone provided sites for chemical modification, and through a variation in the structure, the physical properties, such as the hydrophilicity and solubility, could be affected. With 1,1-di-n-butyl-stanna-2,7-dioxacyclo-4-heptene as the initiator in the ring-opening polymerization of polyesters, a new set of functionalized polyesters was created. The polymerization of epsilon-caprolactone resulted in poly(epsilon-caprolactone) with a double bond incorporated into the structure. The polymers were obtained in a controlled manner with low molecular dispersities. The double bond was previously incorporated into L-lactide polymers, and the two reactions were compared in this study. The conversion of E-caprolactone, with a degree of polymerization of 50, was completed within 140 min, whereas for L-lactide, only a 45% conversion took place in the same period of time. The dispersities were somewhat higher with E-caprolactone because of the higher reaction rate and, therefore, lower selectivity. The incorporated C-C double bond in the polyesters provided a variety of opportunities for further modifications. In this case, the double bond of the L-lactide macromonomers was oxidized into epoxides. Epoxidation was carried out with m-chloroperoxybenzoic acid as a chemical reagent. The conversion of the double bonds into epoxides was completed, and the obtained yields were good (>95%). As a result of the mild reaction conditions, the epoxidation of the double bond was carried out quantitatively without any side reactions.

Keyword
ring-opening polymerization, polyesters, functionalization of polymers, double bond, epoxidation, UNSATURATED SIDE-CHAINS, BACTERIAL POLYESTERS, EPSILON-CAPROLACTONE, BIOMEDICAL APPLICATIONS, CHEMICAL-MODIFICATION, ALIPHATIC POLYESTERS, L-LACTIDE, POLYMERIZATION, POLYMERS
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-13187 (URN)10.1002/pola.10805 (DOI)000188197200007 ()2-s2.0-0742272592 (Scopus ID)
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
4. Controlled synthesis of star-shaped L-lactide polymers using new spirocyclic tin initiators
Open this publication in new window or tab >>Controlled synthesis of star-shaped L-lactide polymers using new spirocyclic tin initiators
2002 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 3, no 4, 684-690 p.Article in journal (Refereed) Published
Abstract [en]

The reaction between pentaerythritol ethoxylate compounds and dibutyltin oxide was developed as a route to synthesize two new spirocyclic tin initiators. The initiators were successfully synthesized and they were characterized by H-1 NMR and differential scanning calorimetry (DSC). The H-1 NMR spectra showed the characteristic signals for the methylene protons in the ether chains. Furthermore, the usefulness of the new initiators was examined in ring-opening polymerizations of L-lactide in chloroform at 60 degreesC. L-Lactide was polymerized at monomer-to-initiator ([M]/[I]) ratios between 20 and 500. The results indicated that the initiation was instantaneous and that the molecular weight distribution was very narrow, <1.13, The number average molecular weight could be controlled by the [M]/[I] ratio, and the yield was very high. H-1 NMR, size exclusion chromatography, and DSC were used to clarify the architecture, The expected results were obtained. The star-shaped polymers had a smaller hydrodynamic volume, and the melting point was lower than that obtained for the corresponding linear poly(L-lactide).

Keyword
LIVING CATIONIC-POLYMERIZATION, RING-OPENING POLYMERIZATION, BLOCK-COPOLYMERS, STANNOUS OCTOATE, POLYLACTONES, PENTAERYTHRITOL, POLYSTYRENE, POLY(L-LACTIDE), MECHANISM, ALKOXIDES
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-13188 (URN)10.1021/bm020009o (DOI)000176716700008 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
5. Polyester hydrogels with swelling properties controlled by the polymer architecture, molecular weight, and crosslinking agent
Open this publication in new window or tab >>Polyester hydrogels with swelling properties controlled by the polymer architecture, molecular weight, and crosslinking agent
2003 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 41, no 9, 1296-1305 p.Article in journal (Refereed) Published
Abstract [en]

Hydrogels of poly(1,5-dioxepan-2-one) and hydrogels of block copolymers of poly(1,5-dioxepan-2-one) and poly(L-lactide) were synthesized. Both star-shaped polymers and linear polymers were polymerized with ring-opening polymerization and crosslinked in situ with a tetrafunctional acid chloride (1,2,3,4-cyclopentane tetracarboxylic acid chloride) or a difunctional acid chloride (succinyl chloride). Different network architectures were synthesized in this way. The initial monomer concentrations and the molecular weights of the macromonomers were also altered. The networks were characterized with H-1 NMR and differential scanning calorimetry, and the swelling abilities of the different hydrogels were investigated in water and dichloromethane. The ratio of the monomer to the crosslinking agent was assessed by the quantification of the signal intensities in the H-1 NMR spectra of the swelled network and agreed with the theoretical crosslinking density. Both the homopolymers of 1,5-dioxepan-2-one and the copolymers of 1,5-dioxepan-2-one and L-lactide swelled to a high degree in water. The swelling properties of the materials could be varied over a broad range by changes in the architecture, molecular weight, and content of the precursor in the network. Star-shaped poly(1,5-dioxepan-2-one) crosslinked with a difunctional acid chloride had the highest degree of swelling among the different homopolymer hydrogels. This network also had the lowest glass-transition temperature because of the flexible units in the structure. The same trends found for the homopolymer hydrogels were also seen in the hydrogels with block copolymers. The hydrogels swelled enormously in dichloromethane, and as in water, the star-shaped copolymer crosslinked with a difunctional acid chloride had the highest degree of swelling.

Keyword
hydrogels, architecture, polyesters, crosslinking, swelling, RING-EXPANSION POLYMERIZATION, POLY(ETHYLENE GLYCOL), EPSILON-CAPROLACTONE, L-LACTIDE, MACROCYCLIC POLYMERIZATION, BIODEGRADABLE NETWORKS, OPENING POLYMERIZATION, POLYLACTONES, 1, 5-DIOXEPAN-2-ONE, INITIATORS
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-13189 (URN)10.1002/pola.10682 (DOI)000182114700012 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved
6. Well-organized phase-separated nanostructured surfaces of hydrophilic/hydrophobic ABA triblock copolymers
Open this publication in new window or tab >>Well-organized phase-separated nanostructured surfaces of hydrophilic/hydrophobic ABA triblock copolymers
2003 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 4, no 5, 1451-1456 p.Article in journal (Refereed) Published
Keyword
ATOMIC-FORCE MICROSCOPY, L-LACTIDE, THIN-FILM, 1, 5-DIOXEPAN-2-ONE, POLY(L-LACTIDE), NANOTOPOGRAPHY, MORPHOLOGIES, CELLS
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-13190 (URN)10.1021/bm0341024 (DOI)000185386900047 ()
Note
QC 20100602Available from: 2010-06-02 Created: 2010-06-02 Last updated: 2017-12-12Bibliographically approved

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