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  • 1.
    Antoni, Per
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Vamvounis, George
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nyström, Daniel
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nyström, Andreas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindgren, Mikael
    Norwegian Univ Sci & Technol, Dept Phys.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Europium confined cyclen dendrimers with photophysically active triazoles2008Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 18, nr 22, s. 2545-2554Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dendrimers up to the fourth generation (G1-G4) were successfully synthesized via the efficient copper catalyzed 1,3-dipolar cycloaddition between primary alkynes and azides (CuAAC), also referred to as a click reaction. The synthetic protocol involved the preparation of presynthesized dendron wedges that subsequently were attached to a tetra-valent alkyne functional cyclen core. These constructed structures integrated stable triazole groups "intra-locked'' between the cyclen and dendron wedges. The incorporation of a lanthanide metal ion, europium, into the interior of all cyclen dendrimers was monitored by FT-IR. Interestingly, the photophysical results showed that the proximate triazole not only acts as a stable linker but also as a sensitizers, transferring its singlet-singlet excitation in the ultraviolet region (270-290 nm) to the partially filled luminescent lanthanide 4f shell. An increase of luminescence decay time from the lanthanide D-5(0) -> F-7(2) emission was observed with increasing dendrimer size, indicating that the shielding effect of the dendron wedges is important for the relaxation of the photo-excitation and energy transfer. To the best of our knowledge, this is the first time a set of dendron wedges have successfully been attached to a cyclen metal ion cage via the versatile click reaction. Furthermore, the produced triazoles intra-locked in close proximity to the macrocycle core elucidated an interesting photophysical function.

  • 2. Hietala, Sami
    et al.
    Nyström, Andreas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Tenhu, Heikki
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Solution Properties of Dendronized Poly(Hydroxy Ethyl Methacrylate) Polymers2006Inngår i: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 44, nr 11, s. 3674-3683Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four generations of dendronized polymers with a methacrylate backbone and hydroxy-functionalized aliphatic polyester dendrons based on 2,2-bis(methylol)propionic acid were studied in solutions by rheological measurements, dynamic light scattering, turbidimetry, and H-1 NMR self-diffusion measurements to reveal the effect of increasing hydrophilicity and molecular size on their solution properties. The studied polymers were interesting new amphiphiles with a hydrophobic main chain and a hydrophilic shell. Evidence of aggregation upon the heating of the first-generation polymer in an aqueous solution was obtained by dynamic light scattering and turbidimetry, reflecting the effect of the hydrophobic polymer backbone, whereas the higher generation polymers did not show aggregation upon heating. Although the dimensions of the polymers were observed to increase with increasing generation, all the polymers exhibited low viscosities and Newtonian flow behavior in both aqueous and dimethyl sulfoxide solutions. The relative viscosities of the polymers in water and dimethyl sulfoxide showed that the conformation of the polymers was somewhat more open in dimethyl sulfoxide, and this led to higher viscosities than those in water, in agreement with the H-1 NMR diffusion measurements, by which the dimensions were found to be larger for the polymers dissolved in dimethyl sulfoxide.

  • 3.
    Nyström, Andreas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Dendrimers and dendronized polymers: synthesis and characterization2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The goal of this work was to synthesize complex macromolecular architectures such as dendrimers and dendronized polymers, and evaluate the effect from the dendrons on the optical and material properties. The work presented in this doctoral thesis, Dendrimers and Dendronized Polymers - Synthesis and Characterization, is divided into one minor and one major part. 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 dendronized poly(hydroxyl ethyl methacylate), dendronized poly(norbornene), and dendronized triblock copolymers, were the pendant dendrons are based on bis-MPA.

    Both free-base and zinc containing dendritic porphyrins was synthesized up to the fifth generation by employing iterative ester coupling utilizing the acetonide protected anhydride of bis-MPA as generic building block.

    First and second generation dendron bearing methacrylates based on 2-hydroxyethyl methacrylate were also synthesized by utilizing the acetonide protected anhydride of bis-MPA, and subsequently polymerized by atom transfer radical polymerization. By adopting a divergent “graft-to” approach starting from the first generation dendronized poly(hydroxyl ethyl methacrylate), well-defined dendronized polymers with acetonide, hydroxyl, acetate and hexadecyl surface functionality were obtained.

    By utilizing the same divergent iterative esterfication, first to fourth generation dendron functionalized norbornenes were synthesized. These monomers were polymerized by ring-opening metathesis polymerization, utilizing either Grubbs´ first or second generation catalyst.

    Acrylate functional first to fourth generation monomers were synthesized by the copper(I) catalyzed “click” coupling of azido functional dendrons and propargyl acrylate. The monomers were polymerized to dendronized triblock copolymers by reversible addition-fragmentation chain transfer polymerization, utilizing a difunctional poly(methyl methacrylate) as macro chain transfer agent.

    The bulk properties of the dendronized poly(hydroxyl ethyl methacrylate) and poly(norbornene) were investigated by dynamic rheological measurements and differential scanning calorimetry. It was found that all the acetonide functional bis-MPA based dendronized polymers had glass transitions temperatures in a similar range. The rheological behaviour showed that for the dendronized polymers having the same backbone length the complex viscosity as a function of functionality was independent of the surface functionality of the polymer. The generation number of the polymer had a profound influence on the complex viscosity, changing form a Newtonian behaviour to a shear thinning behaviour when the generation of the dendrons was increased from two to four. The dendronized poly(norbornene) had increasingly shorter backbone lengths for each generational increase, and for the materials set with comparably lower degree of polymerization, the G’ part of the complex modulus was mostly affected by attaching larger dendrons. In the case of the sample set of higher degree of polymerization, the second, third, and fourth generation samples had similar slopes of the G’ and G” curves, indicating a similar relaxation behaviour.

  • 4.
    Nyström, Andreas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Synthesis and characterization of dendritic architectures2005Licentiatavhandling, med artikler (Annet vitenskapelig)
    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.

  • 5.
    Nyström, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Furo, Istvan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Bulk Properties of Dendronized Polymers with Tailored End-groups emanating from the same Backbone2005Inngår i: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 43, nr 19, s. 4496-4504Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 6.
    Nyström, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Dendronized polymers with tailored surface groups2005Inngår i: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 43, nr 17, s. 3852-3867Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 7.
    Nyström, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Furo, Istvan
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Nyström, Daniel
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Unal, Kerem
    Antoni, Per
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Vamvounis, George
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hawker, Craig
    Wooley, Karen
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Characterization of Poly(norbornene) Dendronized Polymers Prepared by Ring-Opening Metathesis Polymerization of Dendron Bearing Monomers2006Inngår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 39, nr 21, s. 7241-7249Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The preparation and characterization of a series of first to fourth generation dendronized poly-(norbornene)s are presented. The monomers were synthesized in a divergent fashion from 5-norbornene-2-methanol, utilizing the acetonide protected anhydride of 2,2-bis(methylol)propionic acid. The norbornenyl bearing dendrons were polymerized by ring-opening metathesis polymerization, and it was found that the Grubbs' first generation catalyst resulted in polymers with lower polydispersity compared to the materials obtained when employing the second generation catalyst. Two series of first to fourth generation polymers were characterized by DSC, SEC, and dynamic rheological measurements. In addition, it was found that the fourth generation material could form regular, porous membranes and birefringent fibers. The membranes were characterized with atomic force and optical microscopy. The birefringent fibers were analyzed with X-ray diffraction, polarized FTIR, and polarized optical microscopy.

  • 8.
    Nyström, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Dendronized ABA Triblock copolymers by Reversible Addition-Fragmentation Transfer Polymerization2006Manuskript (preprint) (Annet vitenskapelig)
  • 9.
    Nyström, Andreas
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Vestberg, Robert
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Lindgren, Mikael
    Malmström, Eva
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Hult, Anders
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Porphyrin-Cored 2,2-Bis(methylol)propionic Acid Dendrimers2004Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Chemistry of materials, Vol. 16, nr 14, s. 2794-2804Artikkel i tidsskrift (Fagfellevurdert)
    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.

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