| 1. |
- BAKKER, ALBERT, et al.
(författare)
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CONTACT ION-PAIR FORMATION AND ETHER OXYGEN COORDINATION IN THE POLYMER ELECTROLYTES M[N(CF3SO2)(2)](2)PEO(N) FOR M=MG, CA, SR AND BA
- 1995
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 36:23, s. 4371-4378
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Tidskriftsartikel (refereegranskat)abstract
- The polymer electrolytes M[N(CF3SO2)(2)](2)PEO(n) for M = Mg, Ca, Sr and Ba have been investigated using infra-red spectroscopy, differential scanning calorimetry and impedance spectroscopy. The effects of varying concentration (n = 6-40) and temperature (25-95 degrees C) on the contact ion pair formation and cation coordination have been studied. Contact ion pairs are only found for the most concentrated samples (n < 9). Ion pairs occur with two types of structures: one type is found far samples containing Mg2+ and the other for samples with Ca2+, Sr2+ and Ba2+. The conductivities of the samples are discussed in terms of radii and coordination numbers of the cations.
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| 2. |
- Bakker, Albert, et al.
(författare)
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Polymer electrolytes based on triblock-copoly(oxyethylene/oxypropylene/oxyethylene) systems
- 1996
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 37:10, s. 1871-1878
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Tidskriftsartikel (refereegranskat)abstract
- Polymer electrolytes based on triblock copolymers of ethylene oxide (EO)/propylene oxide (PO)/ethylene oxide of moderate molecular weight and narrow block-length distributions, doped with M(CF3SO3)(2) and M[N(CF3SO2)(2)](2) (M = Mg, Ca, Sr and Ba), LiCF3SO3 and LiN(CF3SO2)(2) have been investigated using infrared spectroscopy, differential scanning calorimetry and conductivity measurements. The effects of varying the EO/PO block length, composition and temperature on the phase behaviour, ion-pair formation and conductivity of the polymer electrolytes have been studied. A two-phase microstructure has been observed. Ion pairing occurs for the triflate salts and the amount was found to be sensitive to the relative block sizes rather than the molecular weight of the copolymer. Copyright (C) 1996 Elsevier Science Ltd.
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| 3. |
- Cacialli, F., et al.
(författare)
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Synthesis and characterisation of poly(distyrylbenzene-block-hexa(ethylene oxide)) and its fluorinated analogue - Two new block copolymers and their application in electroluminescent devices
- 2002
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 43:12, s. 3555-3561
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Tidskriftsartikel (refereegranskat)abstract
- Two new soluble block copolymers are reported in which chromophores and hexa(ethylene oxide) units alternate along the polymer backbone. In polymer 1 the chromophore was the distyrylbenzene unit. The polymer was synthesised via the Wittig reaction and the ionization potential of 5.4 ± 0.2 eV was measured by cyclic voltammetry and photoelectron spectroscopy. Polymer 1 showed a high solid-state photoluminescence efficiency (34%) and was used to make efficient (0.5 cd/A) light emitting diodes (LEDs). Polymer 1 was also used in light emitting cells, these showed luminescence in reverse bias and a reduced turn-on voltage compared to the LEDs. Polymer 2, in which the chromophore was dodecafluoro-distryrylbenzene, was prepared via the Horner-Wittig reaction and showed an ionization potential of 6.25 ± 0.15 eV and a solid-state photoluminescence efficiency of 17%. It was used as electron-conducting layer in a LED but failed to give significant electroluminescence. The optical energy gap for both polymers was 3.0 eV. © 2002 Published by Elsevier Science Ltd.
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| 4. |
- Carlmark, Anna E, et al.
(författare)
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Atom transfer radical polymerization of methyl acrylate from a multifunctional initiator at ambient temperature
- 2002
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Ingår i: Polymer. - OXFORD, ENGLAND : ELSEVIER SCI LTD. - 0032-3861 .- 1873-2291. ; 43:15, s. 4237-4242
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Tidskriftsartikel (refereegranskat)abstract
- A multifunctional initiator for ATRP has been synthesized by reacting a hyperbranched polyether, based on 3-ethyl-3-(hydroxymethyl)oxetane, with 2-bromo-isobutyrylbromide. The macroinitiator contained approximately 25 initiating sites per molecule. It was used for the atom transfer radical polymerization of methyl acrylate mediated by Cu(I)Br and tris(2-(dimethylamino)ethyl)amine (Me-6-TREN) in ethyl acetate at room temperature. This yielded a co-polymer with a dendritic-linear architecture. The large number of growing chains from each macromolecule increases the probability of inter-and intramolecular reactions. In order to control these kinds of polymerizing systems and prevent them from forming a gel, the concentration of propagating radicals must be kept low. The polymerizations under these conditions were well controlled. When a ratio of initiating sites-to-catalyst of 1:0.05 was used, the polymers from all of the reactions had a low polydispersity, ranging from 1.1 to 1.4. None of the polymerizations under these conditions gave gelation. Monomer conversions as high as 65% were reached while maintaining control over the polymerization. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 5. |
- Claesson, Hans, et al.
(författare)
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Synthesis and characterisation of star branched polyesters with dendritic cores and the effect of structural variations on zero shear rate viscosity
- 2002
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 43:12, s. 3511-3518
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Tidskriftsartikel (refereegranskat)abstract
- A series of branched polyesters consisting of poly(epsilon-caprolactone) (PCL) (degree of polymerisation: 5-200) initiated from hydroxy-functional cores and end-capped with methylmethacrylate have been prepared. The cores were third-generation hyperbranched polyester, Boltorn, with approximately 32 hydroxyl groups, a third-generation dendrimer with 24 hydroxyl groups and a third-generation dendron with eight hydroxyl groups. Finally, a linear PCL was synthesised as a reference material. All initiators were based on 2,2-bis(methylol) propionic acid (bis-MPA). C-13 NMR spectra of the polymers showed that those with shorter arms contained unreacted hydroxyl groups on the core. Rheological measurements of zero shear rate viscosity, eta(0), showed that the branched polyesters had a considerably lower eta(0) than linear polyester with similar molecular weight. The low melt viscosity and the crystallity produced a theological behaviour suitable for the film formation process for powder coatings. Measurements of mechanical properties of cured films showed that those with low arm molecular weight, M-a, were amorphous while those of high M-a were crystalline.
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| 6. |
- Cordova, A, et al.
(författare)
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Lipase-catalysed formation of macrocycles by ring-opening polymerisation of epsilon-caprolactone
- 1998
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 39:25, s. 6519-6524
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Tidskriftsartikel (refereegranskat)abstract
- Studies were undertaken to gain mechanistic information on lactone ring-opening polymerisation reactions using Candida antarctica lipase B (Novozym 435) as the catalyst and epsilon-caprolactone as the monomer. Polymerisations were performed in organic solvents as well as without solvent at 60 degrees C. Candida antarctica lipase B catalysed concurrently with the intermolecular ring-opening polymerisation, and also the formation of macrocycles by an intramolecular condensation reaction. Candida antarctica lipase B had the highest initial rate of consumption of epsilon-caprolactone (1.2 mu mol mg(-1) min(-1)) in the bulk polymerisation, without solvent. Under these conditions, the highest average M-w, 4701 D, of poly(epsilon-caprolactone) was obtained. There were small amounts of cyclic oligomers present. When comparing the polymerisations performed in dioxane, acetonitrile and THF after 24 h reaction time with the bulk polymerisation, the average M-w of poly(epsilon-caprolactone) [2984, 1297, 1862 D, respectively] and the initial rates of monomer conversion of the enzyme (0.1, 0.05, 0.013 mu mol mg(-1) min(-1), respectively) were lower, however, the formation of cyclic oligomers was high. In dioxane, macrocycles of up to 2623 D corresponding to 23 monomer units were formed, and in acetonitrile there were mostly cyclic oligomers present. (C) 1998 Elsevier Science Ltd. All rights reserved.
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| 7. |
- Ericson, Mats L., et al.
(författare)
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Design and potential of instrumented ultramicrotomy
- 1997
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 38:17, s. 4485-4489
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Tidskriftsartikel (refereegranskat)abstract
- Ultramicrotomes are generally used for preparation of very thin sections for transmission electron microscopy. Recently it has been shown that when the sample holder of the ultramicrotome is instrumented with a force transducer, it is possible to measure the very small sectioning force during sectioning, and calculate the energy dissipated. In the present work, the instrumentation is further improved. The new sample holder, which uses two piezo-electric force transducers can measure two force components simultaneously. It is not only robust and stiff, but it also shows high sensitivity and reproducibility. It is possible to detect sectioning forces lower than 0.1 mN. The method is demonstrated on two amorphous polymers, poly(methyl methacrylate) and epoxy. Fracture energies in the same order of magnitude as theoretical predictions from chemical bond fracture only are recorded. It is therefore suggested that the method of instrumented ultramicrotomy is a useful tool when information on covalent bond density is needed. Potential future applications are identified including research on nano-scale fracture, characterization of molecular anisotropy and developments of the ultramicrotome
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| 8. |
- Ferry, Anders, et al.
(författare)
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Raman, infra-red and d.s.c. studies of lithium coordination in a thermoplastic polyurethane
- 1996
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Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 37:5, s. 737-744
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Tidskriftsartikel (refereegranskat)abstract
- Fourier transform (FT)-Raman and infra-red (i.r.) spectroscopy were utilized to monitor changes in the morphology of a commercial, phase-segregated thermoplastic polyurethane (TPU) as a function of LiClO4 concentration (0.1 to 2.0 mmol/g TPU). Significant changes in both the FT-Raman and the FTi.r. spectra were detected which suggest a competition between hydrogen bonding and lithium cation coordination, especially between the hard segments of the host polymer matrix. A loss in long-range ordering of the hard domain was observed by differential scanning calorimetry with an increase in salt concentration. The ionic conductivity (σ) was found to increase with increasing temperature and salt concentration. For the highest concentration used, σ ranged from a very low value of ∼ 1 x 10-9 S cm-1 at room temperature to ∼ 1 x 10-4 S cm-1 at 130 degrees C.
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| 9. |
- Gallet, G., et al.
(författare)
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Thermal degradation of poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer : comparative study by SEC/NMR, SEC/MALDI-TOF-MS and SPME/GC-MS
- 2002
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 43:4, s. 1081-1094
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Tidskriftsartikel (refereegranskat)abstract
- By comparing size exclusion chromatography/matrix assisted laser desorption ionisation (SEC/MALDI) and SEC/NMR spectra from virgin poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer, we were able to understand the bimodal distribution observed in poloxamer 407. Propylene oxide, isomerised to allyl alcohol during polymerisation, eventually forms a Poly(ethylene oxide-propylene oxide) diblock copolymer when EO is added to the feed. The oxidative thermal degradation of poloxamer 407 at 80 degreesC in air was studied. We found by MALDI that degradation starts after 21 days in the PPO block of the copolymer. This result was confirmed by solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS): The first volatile degradation product to appear is 1,2-propanediol,1-acetate,2-formate. The structure of this molecule suggests that a six-ring intramolecular decomposition reaction of the PPO chain occurs at the very beginning of the polymer breakdown. Thus, the secondary hydroperoxide formed on the PPO chain plays a major role on the thermoxidation of poloxamer materials.
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| 10. |
- Glauser, T, et al.
(författare)
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Electron-beam curing of thick thermoset composite matrices
- 1999
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 40, s. 5297-5302
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Tidskriftsartikel (refereegranskat)abstract
- Electron-beam (EB) curing of two epoxy resins, one acrylated and one methacrylated, has been investigated. The change in thermomechanical properties, such as T-g, and the change of residual unsaturation have been studied as a function of dose. These results, in combination with in situ measurements of the temperature during cure, have shown the importance of sample geometry for the final properties of the thermoset. The thermal history of the sample during cure greatly affects the properties of the cured resin. (C) 1999 Elsevier Science Ltd. All rights reserved.
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