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Synthesis and characterization of dendritic architectures
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The goal of this work was to synthesize different dendritic architectures and evaluate the effect from the dendrons on the material properties. The work presented in this licentiate thesis, Synthesis and Characterization of Dendritic Architectures, is divided into major parts. The first part deals with the synthesis and characterization of two sets of dendritic porphyrins based on 2,2-bis(methylol)propionic acid (bis-MPA). The second part deals with the synthesis and characterization of a series of dendronized polymers based on bis-MPA.

Both free-base and zinc containing dendritic porphyrins were synthesized up to the fifth generation utilizing the acetonide protected anhydride of bis-MPA. The resulting dendrimers were characterized by SEC, NMR, and MALDI-TOF. The dendrimers were found to be well-defined, virtually monodisperse, molecules up to the fourth generation. In the case of the fifth generation dendrimers, some structural defects were observed. The hydrodynamic volume (in THF) of these molecules was calculated using the rotational correlation time, and they were found to be more compact than the corresponding Fréchet-type dendrimers of the same generation.

Macromonomers of the first and second generation were also synthesized utilizing the acetonide protected anhydride of bis-MPA and subsequently polymerized by atom transfer radical polymerization, using a system of N-propyl-2-pyridylmethanamine, Cu(I)Br, and Cu(I)Br2. This system resulted in well-controlled polymerizations with low polydispersity polymers. By adopting a divergent ‘graft-to’ approach, welldefined dendronized polymers with acetonide, hydroxyl, acetate, and hexadecyl functionality respectively, were obtained.

The bulk properties of the dendronized polymers were investigated by differential scanning calorimetry, dynamic-mechanical measurements, and 1H-NMR selfdiffusion. It was found that that increasing the size of the pendant dendron increased the glass transition temperature of the materials. The degree of crystallization of the hexadecyl functional materials was found to decrease with dendron size, most likely due to the reduced flexibility of the backbone prohibiting effective crystallization. The dynamic mechanical measurements revealed that the behavior of the complex viscosity as a function of frequency was independent of functionality. The second and third generation materials were found to have a Newtonian plateau up to a frequency where they become shear-thinning. The fourth generation materials were found to be shearthinning in the frequency range. 1H-NMR self-diffusion measurements revealed that the shape of the acetonide functional dendronized polymers in solution was best described by using a rod-like or prolated ellipsoid model.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 47 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2005:10
Keyword [en]
Biochemistry
Keyword [sv]
Biokemi
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-283OAI: oai:DiVA.org:kth-283DiVA: diva2:8553
Presentation
2005-04-28, sal H1, 10:00
Supervisors
Note
QC 20101216Available from: 2005-07-06 Created: 2005-07-06 Last updated: 2010-12-16Bibliographically approved
List of papers
1. Porphyrin-Cored 2,2-Bis(methylol)propionic Acid Dendrimers
Open this publication in new window or tab >>Porphyrin-Cored 2,2-Bis(methylol)propionic Acid Dendrimers
Show others...
2004 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Chemistry of materials, Vol. 16, no 14, 2794-2804 p.Article in journal (Refereed) Published
Abstract [en]

The synthesis and characterization of dendron-coated porphyrins up to the fifth generation are described. Both free base and zinc-cored tetraphenylporphyrin (TPPH2 and TPPZn) were used, from which the dendrons were divergently grown using the anhydride of acetonide-protected bis-MPA (acetonide-2,2-bis(methoxy)propanoic anhydride). It is shown that a spacer must be attached to the porphyrin to increase the hydrolytic stability and allow synthesis of higher generations. Direct coupling of dendrons to the porphyrins was also investigated but failed to give full substitution of the porphyrin core. The absorption and fluorescence emission data for the TPPZn dendrimers indicate that the porphyrin configuration may change at higher generations. The hydrodynamic volume of the dendrimers is calculated from the polarization anisotropy decay data. It is shown that these bis-MPA dendrimers are significantly smaller than the same generation Frechet-type benzyl ether TPP dendrimer.

Keyword
photoinduced electron-transfer, dendritic polyglutamic porphyrins, site isolation, zinc porphyrin, poly(amide) dendrimers, 3rd-order nonlinearity, efficient synthesis, metal-complexes, star polymers, metalloporphyrins
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5743 (URN)10.1021/cm035354e (DOI)000222550600018 ()2-s2.0-3142676514 (Scopus ID)
Note
QC 20100914Available from: 2006-05-17 Created: 2006-05-17 Last updated: 2011-09-26Bibliographically approved
2. Dendronized polymers with tailored surface groups
Open this publication in new window or tab >>Dendronized polymers with tailored surface groups
2005 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 43, no 17, 3852-3867 p.Article in journal (Refereed) Published
Abstract [en]

A series of polymers tethered with bis-MPA dendrons was synthesized by a combination of divergent growth and atom transfer radical polymerization (ATRP). Macromonomers of first and second generation were synthesized utilizing the acetonide protected anhydride of bis-MPA as the generic esterfication agent. The macromonomers were polymerized in a controlled fashion by ATRP utilizing Cu(I)/Cu(II) and N-propyl-2-pyridylmethanamine as the halogen/ligand system. The end-groups of these polymers were further tailored to achieve hydroxyl, acetate, and aliphatic hexadecyl functionality. With this approach all polymers will emanate from the same backbone, enabling for an evaluation of both the generation and end-group dependent properties. Furthermore, a dendronized tri-block copolymer was synthesized. All materials were analyzed by H-1 and C-13 NMR, as well as size-exclusion chromatography (SEC). The SEC analysis revealed that the molecular weights of the divergently grown dendronized polymers increased with increasing generation while the polydispersity (PDI) was kept low.

Keyword
atom transfer radical polymerization (ATRP), block copolymers, dendronized polymers, macromonomers, 2, 2-bis(methylol) propionic acid (bis-MPA)
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-5744 (URN)10.1002/pola.20846 (DOI)000231369700015 ()2-s2.0-26944487280 (Scopus ID)
Note
QC 20100907Available from: 2006-05-17 Created: 2006-05-17 Last updated: 2010-12-16Bibliographically approved
3. Bulk Properties of Dendronized Polymers with Tailored End-groups emanating from the same Backbone
Open this publication in new window or tab >>Bulk Properties of Dendronized Polymers with Tailored End-groups emanating from the same Backbone
2005 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 43, no 19, 4496-4504 p.Article in journal (Refereed) Published
Abstract [en]

Dendronized polymers with a methacrylate backbone bearing pendant aliphatic polyester dendrons based on 2,2-bis(methylol)propionic acid have been investigated by rheological measurements, differential scanning calorimetry (DSC), size exclusion chromatography (SEC), and H-1 NMR self-diffusion techniques. The change in material properties due to the attachment of larger dendrons and/or different end-groups to a backbone of the same length is investigated. Dendronized polymers of the second to fourth generation with hydroxyl, acetonide, or hexadecyl end-group functionalities have been studied. DSC revealed that the glass transition temperature of the amorphous polymers increases with increasing size of the dendrons, and that the ability for the hexadecyl functional polymers to crystallize decreases with increasing size of dendrons. H-1 NMR self-diffusion and longitudinal relaxation data are consistent with an elongated rod-like model of the polymers in solution. Larger dendrons lead to a larger rod diameter that approximately double when increasing the generation of dendronized polymer from two to four. Rheological measurements demonstrated that the complex viscosity at low frequency increased with dendron size. Independently of the functionality, the second and third generation samples initially showed a Newtonian plateau, followed by a shear thinning region at higher frequencies. The fourth generation samples only showed shear thinning over the whole frequency region.

Keyword
dendronized polymer, size exclusion chromatography, 1H NMR self-diffusion, differential scanning calorimetry, rheology
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5745 (URN)10.1002/pola.20918 (DOI)000231989400018 ()2-s2.0-27744489363 (Scopus ID)
Note
QC 20100901Available from: 2006-05-17 Created: 2006-05-17 Last updated: 2010-12-16Bibliographically approved

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