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Synthesis and Thiol-Ene Photopolymerization of Allyl Ether Functionalized Dendrimers
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-9200-8004
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0003-3201-5138
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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.

Place, publisher, year, edition, pages
2008. Vol. 46, no 4, 1339-1348 p.
Keyword [en]
crosslinking, dendritic allyl-ether, thermosets, thiol-ene photopolymerization, viscoelastic properties
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-9757DOI: 10.1002/pola.22474ISI: 000253221300017Scopus ID: 2-s2.0-38849124254OAI: oai:DiVA.org:kth-9757DiVA: diva2:127757
Note
QC 20100831Available from: 2008-12-10 Created: 2008-12-10 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Dendrimers: Synthesis, Characterization and Use in Thiol-Ene Networks
Open this publication in new window or tab >>Dendrimers: Synthesis, Characterization and Use in Thiol-Ene Networks
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
polymer, molecular physics
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-9763 (URN)978-91-7415-195-4 (ISBN)
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

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Publisher's full textScopushttp://www3.interscience.wiley.com/journal/117874887/abstract?CRETRY=1&SRETRY=0

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Malkoch, MichaelJohansson, Mats K. G.Malmström, Eva E.

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