| 1. |
- Andronova, Natalia, et al.
(författare)
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Potential tissue implants from the networks based on 1,5-dioxepan-2-one and epsilon-caprolactone
- 2005
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Ingår i: Polymer journal. - : Elsevier BV. - 0032-3896 .- 1349-0540. ; 46:18, s. 6746-6755
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of degradable polymeric networks for biomedical applications was performed. Cross-linked films of poly(epsilon-caprolactone) (PCL) and poly(1,5-dioxepan-2-one) (PDXO) having various mole fractions of monomers and different cross-link densities were successfully prepared using 2,2'-bis-(epsilon-caprolactone-4-yl) propane (BCP) as cross-linking agent. Reaction parameters were carefully examined to optimise, the film-formin.,, conditions. Networks obtained were elastomeric materials. easy to cast and remove from the mould. Effect of CL content and cross-link density on the final properties of the polymer network was evaluated. High CL content or degree of cross-linking led to increase in Young's modulus and decrease in elongation at break. An increase in crystalline domains in films having a higher CL content was observed by optical microscopy. A greater thermal stability was observed in films having a high CL content. The hydrophilicity of the materials could be tailored by changing the CL content. The surface of the films became rougher with higher CL content.
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| 2. |
- Ivanov, Alexander, et al.
(författare)
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Photosensitive copolymer of N-isopropylacrylamide and methacryloyl derivative of spyrobenzopyran
- 2002
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Ingår i: Polymer. - 0032-3861. ; 43:13, s. 3819-3823
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Tidskriftsartikel (refereegranskat)abstract
- The copolymer of N-isopropylacrylamide (NIPAM) and methacryloyl derivative of spirobenzopyran (MSBP) with a molecular weight of 21 000 g/mol and the average molar MSBP content of 1.9% was prepared by free radical polymerization. The copolymer displayed its phase transition in water in the temperature range of 30-50 degreesC. UV irradiation of its aqueous solution caused photoinduced transformation of MSBP units into their coloured merocyanine forms, while the cloud point of the irradiated copolymer shifted by ca. 10 degreesC to lower temperatures. During a long-term exposure to daylight (20 days) the copolymer gradually elapsed to its colourless spiropyran form, the process being ca. 100-times slower than that for monomeric MSBP. Due to the slow reverse isomerization of its merocyanine form and low solubility in water at room temperature the UV irradiated copolymer could be quantitatively separated from aqueous solution by centrifugation. (C) 2002 Published by Elsevier Science Ltd.
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| 3. |
- Jannasch, Patric
(författare)
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Ion conducting electrolytes based on aggregating comblike poly(propylene oxide)
- 2001
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Ingår i: Polymer. - 0032-3861. ; 42:21, s. 8629-8635
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Tidskriftsartikel (refereegranskat)abstract
- Solid and gel electrolytes based on comblike poly(propylene oxide) (PPO) have been prepared and studied. The polymer consisted of a polyethylene backbone densely grafted with PPO side chains terminated by hexadecanoyl chain ends. Analysis by impedance spectroscopy of the solid polymer electrolytes containing lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) salt showed ion conductivities of 10(-5.5) S cm(-1) at 20 degreesC. The ion conductivity of polymer gel electrolytes containing 1 M LiTFSI in gamma -butyrolactone (gamma -BL) reached 10(-3.0) S cm(-1) at 20 degreesC with 50 wt% of electrolyte solution added. Thermal analysis showed that the comblike PPO aggregated through microphase separation of the hexadecanoyl units in both the solid and the gel electrolytes. This microphase had multiple melting points in the temperature interval between -45 and 40 degreesC. Furthermore, the crystallisation of gamma -BL was greatly suppressed in gel electrolytes. A study of the gel electrolytes by FT-IR spectroscopy implied that the lithium ions were preferentially coordinated by the PPO grafts, and not by gamma -BL.
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| 4. |
- Jannasch, Patric
(författare)
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Physically crosslinked gel electrolytes based on a self-assembling ABA triblock copolymer
- 2002
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Ingår i: Polymer. - 0032-3861. ; 43:24, s. 6449-6453
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Tidskriftsartikel (refereegranskat)abstract
- Gel electrolytes were prepared by swelling a self-assembling ABA triblock copolymer with different amounts of a solution of I M lithium bis(trifluoromethylsulfonyl)imide salt in gamma-butyrolactone. The triblock copolymer had endblocks of polyethylene (PE) and midblocks of poly(ethylene oxide-co-propylene oxide) (PEOPO), where the former blocks constituted 10 wt% of the copolymer. Thus, the electrolyte solution was contained in physical networks consisting of PEOPO chains interconnected by crystalline PE phase domains. The gels showed a stepwise increase in the ionic conductivity as a consequence of the melting of the PE domains at approximately 100 degreesC. Also, the conductivity at room temperature increased significantly after annealing above this temperature. Block copolymer gels containing 70 wt% of electrolyte solution reached conductivities of 1 mS/cm at 20 degreesC.
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| 5. |
- Jannasch, Patric
(författare)
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Preparation and characterisation of aggregating comblike poly(propylene oxide)
- 2000
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Ingår i: Polymer. - 0032-3861. ; 41:18, s. 6701-6707
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Tidskriftsartikel (refereegranskat)abstract
- Poly(propylene oxide)s with a comblike architecture were prepared by using an ethylene-vinyl alcohol copolymer as a macroinitiator for anionic graft polymerisation of propylene oxide. The densely grafted polymers were subsequently modified by capping the terminal hydroxyl groups with hexadecanoyl chloride to produce aggregating polymers. Dilute solution viscometry showed that the hydroxyl and hexadecanoyl content of the uncapped and capped polymers, respectively, largely determined their state of aggregation in methanol and toluene. Thermal analysis of the uncapped polymers in the solid state showed a decrease in glass transition temperature with increasing average molecular weight of the grafts. Analysis of the capped polymers revealed crystallisation and melting of the hexadecanoyl chain ends in connection with the glass transition of the poly(propylene oxide) phase. It is conceivable that in the solid state the comblike poly(propylene oxide) chains were interconnected by 'micellar-like' microdomains formed by the hexadecanoyl chain ends.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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