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Dendrimers: Synthesis, Characterization and Use in Thiol-Ene Networks
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

 Dendrimers are perfectly branched, well-defined macromolecules with a layered structure and a large amount of peripheral end groups. The high functionality in combination with the possibility of dendrimers to adopt a globular shape at high molecular weights, gives them very unique properties.In this work dendrimers up to fifth generation based on 2,2-bis(methylol)propionic acid (bis-MPA) were synthesized with different core structures. The core moieties were chosen in aspects of functionality and flexibility and the impact of the core on the physical and rheological properties was studied. By using the divergent growth approach dendrimers with acetonide, hydroxyl, allyl ether and methacrylate end groups were obtained.The bulk properties of the acetonide- and hydroxyl- terminated dendrimers were investigated with a rheometer. Temperature sweep tests were performed on the acetonide protected dendrimers in a temperature range of -50 up to 120°C at a constant frequency of 1 Hz. It was observed that the glass transition temperature (Tg) increased with increasing generation and that the modulus dropped without a trace of rubbery plateau for lower generations. This lack of rubbery plateau is due to the absence of entanglements between dendrimers. Interestingly, a small rubbery plateau was visible for generation five which implies enhanced interactions between the dendrimers. This behaviour suggests to be strongly influenced by the structural collapse at higher generations. Further, frequency sweep tests were performed on hydroxyl functional dendrimers at different temperatures. The results revealed Newtonian properties for lower generations and shear-thinning behaviour for higher generations at high frequency.Furthermore, this research involves the creation of well-defined thiol-ene networks by incorporation of allyl ether or methacrylate functional dendrimers in thermosets. This was accomplished by using two trithiols of different molecular weights and react them with the enes under UV irradiation. The thiol-methacrylate crosslinking reaction resulted in inhomogeneous films with and residual unsaturations. The thiol-ene films based on allyl ether dendrimers, on the contrary, resulted in homogeneous films with intermolecular couplings between the ene and the thiol being the dominant mode of polymerization.  

Abstract [sv]

Dendrimerer är perfekt grenade, väldefinierade molekyler med en struktur indelad i lager och med ett stort antal ändgrupper. Dendrimerer har, på grund av sina många funktionella grupper och sin förmåga att vid höga molekylvikter anta en mer sfärisk struktur, väldigt speciella egenskaper. Dendrimerer upp till femte generation, baserade på 2,2-dimetylolpropan syra (bis-MPA), har syntetiserats med olika typer av kärnstrukturer. Kärnorna valdes med avseende på funktionalitet och flexibilitet, och strukturens påverkan på dendrimerernas fysikaliska och reologiska egenskaper undersöktes. Dendrimerer med acetonid-, hydroxyl-, allyleter- samt metakrylatändgrupper syntetiserades genom att använda en divergent syntesmetod. De hydroxyl- och acetonidfunktionella dendrimerernas reologiska egenskaper i bulk karakteriserades med en reometer. De acetonidskyddade dendrimererna karakteriserades med temperatursvep i ett intervall mellan -50 °C och 120°C och med en konstant frekvens på 1 Hz. Analyserna visade att glastransitionstemperaturen (Tg) ökade med ökande generation och att dendrimerer av lägre generation inte uppvisade någon gummiplatå. Anledningen till detta är att det inte förekommer några kedjeintrasslingar mellan dendrimerer. Dock uppvisar femte generationens dendrimerer liten gummiplatå vilket pekar på ökade interaktioner mellan dem. Detta beteende påverkas av att dendrimerna kollapsar vid höga generationer och att förändringen i strukturen tydligt påverkar interaktionerna. Hydroxylfunktionella dendrimererna karaktäriserades med frekvessvep vid olika temperaturer. Det visade sig att lägre generationer uppvisar Newtonskt beteende medan högre generationer visar sig vara skjuvförtunnande vid höga frekvenser. Som en ytterligare del i detta projekt skapades väldefinierade tiol-en nätverk genom att reagera allyleter och metakrylat-funktionella dendrimerer med två trifunktionella tioler av olika molekylvikt. Reaktionerna initierades med UV-ljus. Tiol-metakrylat filmerna visade på en hög andel homopolymerisation vilket resulterade i inhomogent tvärbundna nätverk med ett stort antal oreagerade grupper. Tiol-allyleter filmerna visade uppvisade däremot homogena nätverk med en liten andel homopolymerisation.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , 76 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:47
Keyword [en]
polymer, molecular physics
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-9763ISBN: 978-91-7415-195-4 (print)OAI: oai:DiVA.org:kth-9763DiVA: diva2:127775
Public defence
2008-12-19, F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100831Available from: 2008-12-10 Created: 2008-12-10 Last updated: 2010-08-31Bibliographically approved
List of papers
1. Synthesis and Thiol-Ene Photopolymerization of Allyl Ether Functionalized Dendrimers
Open this publication in new window or tab >>Synthesis and Thiol-Ene Photopolymerization of Allyl Ether Functionalized Dendrimers
Show others...
2008 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 46, no 4, 1339-1348 p.Article in journal (Refereed) Published
Abstract [en]

Well-defined, allyl-ether functional, first-generation dendrimers have been synthesized. The convergent growth approach was utilized, using the anhydride of the allyl-ether terminated building block. Three different core moieties were used: trimethylolpropane, trisphenol, and ditrimethylolpropane. The coupling reactions proceeded in good yields and all compounds were characterized by NMR, MALDI-TOF, and SEC. The allyl-terminated dendrimers were crosslinked by thiol-ene chemistry, using a multifunctional thiol, TriThiol, to give clear and smooth films. The photopolymerization was conducted in the presence of a photoinitiator, Irgacure 651, and no traces of either allyl-ether groups or thiols were observed by FT-Raman after cure. All crosslinked films were characterized with respect to mechanical (DMA) and thermal (DSC) properties. It was found that homogeneous networks were formed and that the core functionality and structure had little effect on the network properties.

Keyword
crosslinking, dendritic allyl-ether, thermosets, thiol-ene photopolymerization, viscoelastic properties
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-9757 (URN)10.1002/pola.22474 (DOI)000253221300017 ()2-s2.0-38849124254 (Scopus ID)
Note
QC 20100831Available from: 2008-12-10 Created: 2008-12-10 Last updated: 2017-12-14Bibliographically approved
2. Dendrimers in Thiol-ene Crosslinked Networks and the Effect on Subsequent Generations on Thermoset Properties
Open this publication in new window or tab >>Dendrimers in Thiol-ene Crosslinked Networks and the Effect on Subsequent Generations on Thermoset Properties
2009 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 47, no 2, 589-601 p.Article in journal (Refereed) Published
Abstract [en]

A series of well-defined allyl-ether functionalized polyester dendrimers has been synthesized via the divergent approach using traditional esterification reactions. Two commercially available trifunctional thiols, trimethylolpropane tri(3-mercaptopropanoate) (TRIS) and ethoxylated trimethylolpropane tri(3-mercaptopropanoate) (ETTMP), were incorporated with the dendrimers into the thiol-ene polymer networks. The thiol-ene reactions were conducted at room temperature and cured by UV light without the addition of photoinitiatior. Highly crosslinked films were obtained and characterized with respect to mechanical (DMA) and thermal (DSC and TGA) properties.

Keyword
allyl-ethers, conversion, crosslinking, dendrimers, networks, thermosets, thiol-ene chemistry
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-9758 (URN)10.1002/pola.23176 (DOI)000262326400023 ()2-s2.0-58349112960 (Scopus ID)
Note
QC 20100831. Uppdaterad från in press till published (20100831).Available from: 2008-12-10 Created: 2008-12-10 Last updated: 2017-12-14Bibliographically approved
3. Synthesis and Physical and Rheological Characterization of Aliphatic Polyester Dendrimers with Different Core Structures
Open this publication in new window or tab >>Synthesis and Physical and Rheological Characterization of Aliphatic Polyester Dendrimers with Different Core Structures
2008 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835Article in journal (Other academic) Submitted
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-9759 (URN)
Note
QS 20120315Available from: 2008-12-10 Created: 2008-12-10 Last updated: 2017-12-14Bibliographically approved
4. Methacrylated Dendrimers in Thiol-Methacrylate Networks and the Effect of Conversion on the Thermoset Properties
Open this publication in new window or tab >>Methacrylated Dendrimers in Thiol-Methacrylate Networks and the Effect of Conversion on the Thermoset Properties
2009 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 47, no 21, 5815-5826 p.Article in journal (Refereed) Published
Abstract [en]

A series of well-defined methacrylate-functionalized polyester dendrimers based on 2,2-bis(methylol)propionic acid (bis-MPA) has been synthesized divergently. The thermal properties and conversion of the methacrylate functional dendrimers are investigated along with the structure-property relationship of networks composed of the methacrylate dendrimers and two commercially available trifunctional thiols, trimethylolpropane tri(3-mercaptopropanoate) (TRIS) and ethoxylated trimethylolpropane tri(3-mercaptopropanoate) (ETTMP). The thiol-methacrylate reactions were conducted at room temperature, under ambient conditions, and triggered by UV light in the presence of a photoinitiator. Crosslinked films were obtained and characterized with respect to conversion (FT-Raman) and thermal (DSC and TGA) properties.

Keyword
conversion, endrimers, networks, thermogravimetric analysis, thiol-methacrylate films, acrylate photopolymerizations, dendritic macromolecules, ene, photopolymerization, aliphatic polyesters, physical-properties, oxygen, inhibition, melt viscosity, kinetics, behavior, functionalization
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-18950 (URN)10.1002/pola.23625 (DOI)000271669700023 ()2-s2.0-70349759683 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
5. Physical and Rheological Behaviour of Aliphatic Polyester Dendrimers in Bulk and the Effect of Polar End Groups
Open this publication in new window or tab >>Physical and Rheological Behaviour of Aliphatic Polyester Dendrimers in Bulk and the Effect of Polar End Groups
(English)Manuscript (Other academic)
Keyword
polyester dendrimers, melt rheology 2, 2-bis(methylol)propionic acid (bis-MPA), viscoelastic properties
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-9762 (URN)
Note
QC 20100831Available from: 2008-12-10 Created: 2008-12-10 Last updated: 2010-08-31Bibliographically approved

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