| 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. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- Johansson, A, et al.
(författare)
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Diffusion and ionic conductivity in Li(CF3SO3)PEG(10) and LiN(CF3SO2)(2)PEG(10)
- 1996
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Ingår i: Polymer. - : Elsevier. - 0032-3861. ; 37:8, s. 1387-1393
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Tidskriftsartikel (refereegranskat)abstract
- Self-diffusion of the cation, the anion and the polymer chain in the low-molecular-weight polymer electrolyte systems Li(CF3SO3)PEG(10) and LiN(CF3SO2)(2)PEG(10) has been studied as a function of temperature using nuclear magnetic resonance spectroscopy.
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| 8. |
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| 9. |
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| 10. |
- Laihonen, Sari J., et al.
(författare)
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Crystal structure and morphology of melt-crystallized poly(propylene-stat-ethylene) fractions.
- 1997
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 38:2, s. 371-377
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Tidskriftsartikel (refereegranskat)abstract
- Crystallinity, crystal structure and lamellar thickness in melt-crystallized samples of poly(propylene-stat-ethylene) fractions with 2.7–11.0 mol% ethylene comonomer and of approximately constant tacticity were assessed by wide- and small-angle X-ray scattering, differential scanning calorimetry and infra-red spectroscopy. Most of the samples were crystallized under isothermal conditions at 373 K. In comparison with an isotactic homopolymer of polypropylene, the copolymers showed lower crystallinity, melting enthalpy and average length of 3/1 helices, a slightly larger unit cell, a longer long period and an invariant lamellar thickness. The X-ray crystallinity of the copolymers remained approximately constant with increasing ethylene content, whereas the γ-crystallinity increased and the heat of fusion decreased moderately. It is suggested that the ethylene units are partially included in the crystals, and that this causes the invariance in crystallinity and crystal thickness. The observed gradual decrease in average 3/1 helix length with increasing ethylene content as assessed by infra-red spectroscopy is in accordance with this suggestion.
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