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  • 1. Bouit, Pierre-Antoine
    et al.
    Westlund, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Feneyrou, Patrick
    Maury, Olivier
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Andraud, Chantal
    Dendron-decorated cyanine dyes for optical limiting applications in the range of telecommunication wavelengths2009In: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 33, no 5, p. 964-968Article in journal (Refereed)
    Abstract [en]

    Cyanine dyes decorated with 2,2-bis(methylol) propionic acid (bis-MPA) based dendrons up to third generation were synthesized. Dendrons were attached to the chromophore using a "click chemistry'' reaction. Photophysical characterizations of these dyes show intense absorption and emission in the near-infrared (NIR), while nonlinear transmission experiments of the dendron-decorated chromophores indicate that properties in the IR of the parent dyes are conserved. This synthetic approach is a crucial preliminary step towards the preparation of solid functional materials for optical limiting (OL) applications in the IR.

  • 2. Glimsdal, E.
    et al.
    Carlsson, M.
    Eliasson, B.
    Westlund, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindgren, M.
    Photo-physical properties and OPL of some new longer thiophenyl-containing arylalkynyl Pt(II) compounds2007In: Optical Materials in Defence Systems Technology IV, SPIE - International Society for Optical Engineering, 2007, p. -M7400Conference paper (Refereed)
    Abstract [en]

    The photo-physical and optical power limiting (OPL) properties of several new thiophenyl-containing arylalkynyl Pt(II) complexes with longer arylalkynyl groups, named ATP3, ATP4, ATP6 and ATP7 were studied. Thiophene units were introduced into the structure as an attempt to modify photo-physical properties and OPL capability. The new compounds have their thiophene rings either close to the Pt-atom (ATP7), in the middle of the chain (ATP3), or at the terminal end (ATP4). The measurement results were compared with those of the earlier studied PE3 compound. ATP6 is similar to ATP4, but with methoxy groups in the arylalkynyl ligands. Just as PE3, all thiophenyl derivatives showed large intersystem crossing capabilities and triplet phosphorescence, thus having the potential of large nonlinear absorption and good OPL performance. All compounds are characterized by absorption and emission spectra, quantum yield, luminescence decay (fluorescence and phosphorescence) and two-photon absorption capabilities at 780 nm, and compared to the properties of the PE3 compound. Also analogous triazole-containing compounds, abbreviated Z1, Z2 and Z3, were studied in the same way, and compared to the earlier studied Pt1-G1 compound. The OPL performance of all compounds were measured, and clamping levels of approximately 2.5 to 5 μJ pulse energy from 30 mM (ATP) and 50 mM (triazole) concentration samples were found. All compounds possess high transmission in the visible region and fluorescence quantum yields in the order of 10-2 (ATP) and 10-3 (triazoles).

  • 3. Glimsdal, E.
    et al.
    Westlund, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindgren, M.
    Photo-physical properties and triplet-triplet absorption of platinum(II) acetylides in solid PMMA matrices2009In: Nonlinear Optics and Applications III, SPIE - International Society for Optical Engineering, 2009, p. 73540H-Conference paper (Refereed)
    Abstract [en]

    Because of their strong nonlinear optical properties, Platinum(II) acetylides are investigated as potential chromophores for optical power limiting (OPL) applications. The strong excited state absorption and efficient intersystem crossing to the triplet states in these materials are desired properties for good OPL performance. We recently reported on OPL and photo-physical properties of Pt(II)-acetylide chromophores in solution, modified with thiophenyl or triazole groups. [R. Westlund et al. J. Mater. Chem. 18, 166 (2008); E. Glimsdal et al. Proc. SPIE 6740, 67400M (2007)] The chromophores were later incorporated into poly(methyl-methacrylate) (PMMA) glasses. A variety of doped organic solids were prepared, reaching concentrations of up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices proved that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photo-physical properties (absorption, emission and inter-system crossing) observed for the solute molecules in THF are maintained also in the solid state. In particular, the phosphorescence lifetime stays in the order of μs to ms, just as in the oxygen evacuated liquid samples. Also, the wavelength dependence and time-dynamics of the triplet absorption spectra of the dyes, dissolved in THF solution and dispersed in solid PMMA matrices, were investigated and compared. Ground state UV absorption spectra between 300 and 420 nm have corresponding broad band visible triplet-triplet absorption between 400 and 800 nm. The triplet state extinction coefficients were determined to be in the order of 104 M-1cm-1.

  • 4.
    Lindgren, Mikael
    et al.
    Department of Physics, Norwegian University of Science and Technology.
    Minaev, Boris
    Department of Physics, Norwegian University of Science and Technology.
    Glimsdal, Eirik
    Department of Physics, Norwegian University of Science and Technology.
    Vestberg, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Westlund, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Electronic states and phosphorescence of dendron functionalized platinum(II) acetylides2007In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 124, no 2, p. 302-310Article in journal (Refereed)
    Abstract [en]

    The photophysical properties of bis((4-(phenylethynyl)phenyl)ethynyl)bis(tributylphosphine) platinum(II) with 2,2-bis(methylo])propionic acid (bis-MPA) dendritic substituents were studied. The fluorescence emission decay upon excitation in the UV (typically 350-380 nm) was rapid, in the order of I ns or shorter. In oxygen-saturated tetrahydrofuran solvent, the phosphorescence decay time was in the order of 200 ns. Bright phosphorescence at 530 nm was found for dendrimers under certain conditions. The associated phosphorescence decay time considerably increased to above 100-200 mu s at higher concentrations (30-100 mu M), and in oxygen-evacuated samples. Thus, it was clarified that the strongest triplet quenching was caused by oxygen dissolved in the sample, since it was possible to reversibly go between the bright and quenched phosphorescent state by freeze-thaw pumping cycles. The bright phosphorescence formed spontaneously for the cases with the larger dendritic substituents is implying a chromophore protecting effect. From time-dependent density functional calculations, the electronic structure of a few low-lying singlet and triplet states are discussed. A new mechanism for efficient triplet state formation and phosphorescence of Pt-ethynyls is proposed. Here, a fast relaxation via internal conversion takes the excited population of the dominant pi -> pi*, excitation into a lower singlet state of ligand-to-metal charge transfer character of pi sigma* type. This allows an efficient inter system crossing to the triplet state manifold.

  • 5.
    Rahm, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Westlund, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Eldsäter, Carina
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Tri-Block Copolymers of Polyethylene Glycol and Hyperbranched Poly-3-ethyl-3-(hydroxymethyl)oxetane Through Cationic Ring Opening Polymerization2009In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 47, no 22, p. 6191-6200Article in journal (Refereed)
    Abstract [en]

    Tri-block copolymers of linear poly(ethylene glycol) (PEG) and hyperbranched poly-3-ethyl-3-(hydroxymethyl)oxetane (poly-TMPO) are reported. The novel dumb-bell shaped polyethers were synthesized in bulk with cationic ring-opening polymerization utilizing BF3OEt2 as initiator, via drop-wise addition of the oxetane monomer. The thermal properties of the materials were successfully tuned by varying the amount of poly-TMPO attached to the PEG-chains, ranging from a melting point of 54 degrees C and a degree of crystallinity of 76% for pure PEG, to a melting point of 35 degrees C and a degree of crystallinity of 12% for the polyether copolymer having an average of 14 TMPO units per PEG chain. The materials are of relatively low polydispersity, with M-n/M-w ranging from 1.2 to 1.4. The materials have been evaluated for usage with the energetic oxidizer ammonium dinitramide.

  • 6.
    Vestberg, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Westlund, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Eriksson, Anders
    Department of Functional Materials, Swedish Defence Research Agency.
    Lopes, Cesar
    Department of Functional Materials, Swedish Defence Research Agency.
    Carlsson, Marcus
    Department of Chemistry, Organic Chemistry, Umeå University.
    Eliasson, Bertil
    Department of Chemistry, Organic Chemistry, Umeå University.
    Glimsdal, Eirik
    Department of Physics, Norwegian University of Science and Technology.
    Lindgren, Mikael
    Department of Physics, Norwegian University of Science and Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Dendron Decorated Platinum(II) Acetylides for Optical Power Limiting2006In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 39, no 6, p. 2238-2246Article in journal (Refereed)
    Abstract [en]

    The effect of dendritic substituents on a nonlinear optical chromophore for optical power limiting (OPL) has been investigated. Synthesis and characterization of bis((4-(phenylethynyl)phenyl)ethynyl)bis-(tributylphosphine) platinum(II) with dendritic end groups are described. Polyester dendrimers up to the fourth generation were grown divergently using the anhydride of 2,2-bis(methylol)propionic acid (bis-MPA). The introduction of the dendritic moieties onto the NLO chromophore enables further processing of the materials using polymeric and related techniques. OPL measurements performed at 532, 580, and 630 nm show that the OPL properties improve with increasing size of the dendritic substituent. It is also shown that the addition of the dendrons increase the OPL as compared to the nondecorated bis((4-(phenylethynyl)phenyl) ethynyl)bis-(tributylphosphine)platinum(II). By use of femtosecond z-scan measurements carried out at different pulse-repetition frequencies, it is shown that the two-photon absorption cross section is ∼10 GM. Using pulse repetition frequencies (100 kHz-4.75 MHz) so that the time between the pulses is comparable with the triplet excited lifetime, the z-scans become dominated by excited-state absorption of excited triplet states.

  • 7.
    Westlund, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nonlinear Absorbing platinum(II) Acetylides for Optical Power Limiting Applications2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    During the past few decades, laser technology has had a strong impact on our society, providing important contributions to materials processing, data storage, communications, medicine, and defense applications. However, the progress in laser technology has also brought about the development of harmful portable high‐power lasers and tactical laser weapons. As a result, the hazard of being blinded by lasers (accidentally or from hostile use) has increased significantly. Hence, the need for protection against lasers has emerged. In order to protect optical sensors against harmful laser radiation, materials that absorb high intensity light, such as nonlinear absorbing chromophores, are employed. The concept of controlling the intensity of an optical light beam is usually referred to as optical power limiting and can be used efficiently in sensor protection devices.In this thesis, various nonlinear absorbing platinum(II) acetylides have been synthesized and characterized regarding their photophysical and optical limiting properties. Dendronized platinum(II) acetylides were prepared in order to evaluate the site isolation effect offered by the dendritic surrounding. The photophysical measurements reveal that the dendritic encapsulation enhances the phosphorescence, increases the luminescence lifetimes, and improves the optical limiting performance due to reduced quenching of the excited states.Triazole‐containing chromophores were synthesized using click chemistry to achieve functionalized platinum(II) acetylides. It was found that the position of the triazole unit affects the photophysical properties of these chromophores. The most promising results were obtained for the chromophore with the triazole located at the end of the conjugation where it may act as an electron donor, thus contributing to improved two‐photon absorption.A branched platinum(II) acetylide was also prepared in order to investigate the effect of multiple conjugated arms as well as multiple heavy atoms within the same molecule on the optical limiting performance. The star shaped chromophore reached the lowest clamping level of all compounds included in this thesis and constitutes a highly suitable chromophore for optical power limiting applications.The nonlinear absorbing chromophores were also incorporated into novel solid state materials based on PMMA. The actual device fabrication of doped organic glasses as optical limiters for sensor protection is presented, and their optical limiting performance is reported. The obtained organic glasses can reduce the transmission of high intensity light by 97 %.

  • 8.
    Westlund, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hult, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Saez, Isabel M.
    Grafting liquid crystalline polymers from cellulose substrates using atom transfer radical polymerization2007In: Soft Matter, ISSN 1744-683X, Vol. 3, no 7, p. 866-871Article in journal (Refereed)
    Abstract [en]

    Immobilizing liquid crystalline polymers on cellulose generates new possibilities of accomplishing addressable/ responsive bio-based substrates. In this paper we report on our first steps to combine the electro-optic properties of liquid crystals with the versatility of paper as a displaying substrate. Electric current or magnetic fields can be used to manipulate the orientation of liquid crystals and thereby change the appearance and the properties of the material. Atom transfer radical polymerization ( ATRP) can be used successfully to graft polymers from solid substrates in a controlled manner. In this study it is shown that the grafting of a liquid crystalline monomer, 11-(4'-cyanophenyl-4 ''-phenoxy) undecyl acrylate, onto cellulose by ATRP is possible, and that thicker films can be obtained by using PMA as a spacer in between the cellulose and the liquid crystalline block. The cellulose fibers become highly hydrophobic subsequent to grafting and the liquid crystalline polymer possesses mesophases accessible for further processing.

  • 9.
    Westlund, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Glimsdal, E.
    Lindgren, M.
    Lopes, C.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Click Chemistry and Dendrimer Synthesis as Tools for Designing Efficient Optical Power Limiting Platinum(II) Acetylides2007In: Polymer Preprints, ISSN 0032-3934, Vol. 48, no 2, p. 537-538Article in journal (Refereed)
  • 10.
    Westlund, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Glimsdal, Eirik
    Department of Physics, Norwegian University of Science and Technology.
    Lindgren, Mikael
    Department of Physics, Norwegian University of Science and Technology.
    Vestberg, Robert
    Materials Research Laboratory, University of California, Santa Barbara.
    Hawker, Craig
    Materials Research Laboratory, University of California, Santa Barbara.
    Lopes, Cesar
    Department of Functional Materials, Swedish Defence Research Agency.
    Malmström, Eva E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Click Chemistry for Photonic Applications: Triazole-Functionalized Platinum(II) Acetylides for Optical Power Limiting2008In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 18, no 2, p. 166-175Article in journal (Refereed)
    Abstract [en]

    Three different triazole-containing platinum(ii) acetylide compounds were synthesized by click chemistry and evaluated for their use in optical power limiting (OPL) applications. The triazole unit was incorporated at three different positions within, or at the end of, the conjugation path of the chromophore. The aim is to explore the possibilities of using click chemistry to prepare dendronized chromophores, and to evaluate how the triazole structure affects the photophysical properties and the optical power limiting abilities of these acetylide compounds. It is shown that the concept of click chemistry can be used to attach branched monomer units to ethynyl-phenyl arms by Huisgen 1,3-dipolar cycloaddition, forming triazole units within the chromophore. Photophysical characterization of these triazole-containing materials shows an absorption maximum within the UV-A region and emission through both fluorescence and phosphorescence. Bright phosphorescence was emitted from argon purged samples, and decay measurements thereof showed triplet lifetimes of up to 100 μs. The results from the photophysical characterization suggest that the triazole does break the conjugation path, and in order to gain maximum optical limiting the triazole needs to be placed at the end of the conjugation. All three investigated triazole-containing platinum(ii) acetylides show good optical power limiting at 532 nm (10 ns pulse, f/5 set-up, 2 mm cells). The most efficient compound, with the triazole positioned at the end of the conjugation, reaches a defined clamping level of 2.5 μJ for a sample with a concentration of 50 mM in THF and a linear transmission above 80% at 532 nm. These data can be compared to the OPL properties of Zn-based porphyrins or derivatized thiophenes, reaching clamping levels of 6-15 μJ.

  • 11.
    Westlund, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Malmström, Eva E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lopes, Cesar
    Öhgren, Johan
    Rodgers, Thomas
    Saito, Y.
    Kawata, S.
    Glimsdal, E.
    Lindgren, Mikael
    Efficient Nonlinear Absorbing Platinum(II) Acetylide Chromophores in Solid PMMA Matrices2008In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 18, no 13, p. 1939-1948Article in journal (Refereed)
    Abstract [en]

    Platinum(II) acetylides were incorporated into poly(methyl methacrylate) (PMMA) glasses to obtain solid-state nonlinear optical devices. We report on device fabrication, structural, chemical, and mechanical properties, as well as the optical limiting capabilities of the final solids. Two different guest-host systems are presented: 1) Dye molecules functionalized to be readily dispersed in methyl methacrylate (MMA) and subsequent in situ polymerization of the MMA yielding solid PMMA host matrices. 2) Dye molecules functionalized to copolymerize with MMA forming covalent bonds between the guest and the PMMA host matrix. A range of doped organic solids were prepared, reaching concentrations up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices indicate that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photophysical properties observed for the same solute molecules in THF are maintained also in the solid state. Optical power limiting (OPL) characterization reveal clamping levels for the dyes nonbonded to the solid host being less than 4 μJ at pulse energies up to 110 μJ at 532 nm (f/5 arrangement and 5 ns pulses), which is comparable to the performance of similar dyes in THF solutions. In contrast, the highly crosslinked solid possesses a higher clamping level (8 μj) at the same nominal concentration.

  • 12.
    Westlund, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hoffmann, Markus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Vestberg, Robert
    Hawker, Craig
    Glimsdal, Eirik
    Lindgren, Mikael
    Norman, Patrick
    Eriksson, Anders
    Lopes, Cesar
    Multi-functionalized platinum(II) acetylides for optical power limiting2006In: Optical Materials in Defence Systems Technology III / [ed] Grote JG; Kajzar F; Lindgren M, SPIE-INT SOC OPTICAL ENGINEERING , 2006, Vol. 6401, p. U87-U94Conference paper (Refereed)
    Abstract [en]

    Preliminary results on the optical power limiting properties of platinum(II) acetylides containing triazole units are presented. It is shown that the triazole units give a positive contribution to the limiting abilities of the platinum(H) acetylide and that this modified chromophore could have potential use in sensor protection devices. Moreover, this paper discusses how the versatile building block 2,2-bis(methylol)propionic acid (bis-MPA) can be used advantageously to functionalize nonlinear optical (NLO) platinum(H) acetylides. The bis-MPA units can be used to prepare dendritic substituents offering site isolation to the chromophore leading to improved clamping. The bis-MPA functionalization also improves the solubility of the platinum(H) acetylides in many organic solvents. The preparation of solid-state optical power limiters, where the NLO chromophore is inserted in an optically transparent matrix, is addressed. Again, the bis-MPA unit can be employed to increase the number of accessible end-groups to which matrix-compatible species can be attached. It is concluded that the hydroxy-functional platinum(II) acetylides can be modified to fit almost any matrix, organic or inorganic. Finally, depending on functionalization, it is possible to prepare doped glasses where the chromophore is either embedded in the matrix, or covalently bonded to the matrix.

  • 13.
    Westlund, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Vestberg, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Glimsdal, Eirik
    Lindgren, Mikael
    Lopes, Cesar
    Malmström, Eva E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Synthesis and Characterization of a 3-Arm Star Platinum(II) Acetylide Chromophore Targeted for Optical Limiting ApplicationsIn: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041Article in journal (Other academic)
1 - 13 of 13
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