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61.
Hatzipanayioti Despina Karaliota Alexandra Kamariotaki Mary Veneris Antony Falaras Polykarpos 《Transition Metal Chemistry》1998,23(4):407-416
The electrochemical and spectroscopic behaviour of 2,3-dihydroxybenzoic acid (2,3-DHBA) and its oxidized forms have been studied in dimethyl sulfoxide solutions under aerobic and anaerobic conditions. The products resulting from the reaction with manganese(II) (in dimethyl sulfoxide) are also studied by cyclic voltammetry, u.v–vis., n.m.r. and e.s.r. spectroscopies. Under anaerobic conditions the anions of the ligand form stable complexes with manganese(II) and (III) of MnL2 type, while in the presence of air the oxidized forms of the ligand react with manganese(II) to give mixed-valence species. The chemical stability of the semiquinone and its manganese complexes in addition to its photosensitivity is noteworthy. Calculations show that the electrogenerated manganese(III)–(2,3-DHB–semiquinone) system is stable, but redox-active and can undergo a two-electron exchange (per monomer). The dimeric (or oligomeric) species should be good candidates for water oxidation studies. 相似文献
62.
Viktor Yu. Kramarenko Tetyana A. Shantalil Iryna L. Karpova Kateryna S. Dragan Eleonora G. Privalko Valery P. Privalko Daniel Fragiadakis Polycarpos Pissis 《先进技术聚合物》2004,15(3):144-148
Polyimide (PI) nanocomposites prepared by the in situ generation of crosslinked organosilicon nanophase (ON) through the sol‐gel process were characterized by densities, thermally stimulated depolarization currents and dielectric relaxation spectroscopy. Both a looser molecular packing of PI chain fragments adjacent to the ON and a loose inner structure of the spatial aggregates of ON were assumed to be responsible for a non‐additive decrease of the experimental values of dielectric permittivity for the nanocomposites. The pattern of composition dependence of the apparent dielectric permittivity of the ON suggested a probability of a morphological change around the composition PAAS/MTS = 100/16 (presumably, a sort of percolation transition from small‐size, individual clusters into large‐size, infinite clusters). Thus, PI reinforced with the sol‐gel derived nanophase may have a reasonably good potential as low dielectric permittivity materials. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
63.
Thermal
analysis of thermoplastic elastomers based on recycled polyethylenes and ground
tyre rubber 总被引:2,自引:0,他引:2
O. Grigoryeva A. Fainleib A. Tolstov P. Pissis A. Spanoudaki A. Vatalis C. Delides 《Journal of Thermal Analysis and Calorimetry》2006,86(1):229-233
Thermal stability
and phase structure of thermoplastic elastomers (TPEs) based on post-consumer
materials such as recycled lowor high-density polyethylene and ground tyre
rubber (GTR) were investigated by using TG, DSC and DMTA analysis. Preliminary
reclamation of GTR leads to enhancement of compatibility between polyethylene
matrix and dispersed GTR particles. 相似文献
64.
Interaction between water and polymer chains in poly(hydroxyethyl acrylate) hydrogels 总被引:2,自引:0,他引:2
M. Monleón Pradas J. L. Gómez Ribelles A. Serrano Aroca G. Gallego Ferrer J. Suay Antón P. Pissis 《Colloid and polymer science》2001,279(4):323-330
Polymer networks of different cross-linking densities were prepared by copolymerisation of hydroxyethyl acrylate and ethylene
glycol dimethacrylate. The average molecular weight between cross-links as well as the polymer chain mobility were characterised
by means of dynamic–mechanical spectroscopy. Equilibrium sorption isotherms and the water uptake in immersion in liquid water
allowed the determination of the Flory–Huggins interaction parameter between water molecules and polymer chain segments, which
decreased with the water activity in the hydrogel and increased with the cross-linking density as a consequence of the hydrophobic
character of the cross-linking agent. Dynamic sorption and desorption experiments were used to determine the diffusion coefficient.
Received: 11 November 1999 Accepted: 28 July 2000 相似文献
65.
Emmanuel Logakis Christos Pandis Vasilios Peoglos Polycarpos Pissis Charalampos Stergiou Jürgen Pionteck Petra Pötschke Matej Mičušík Mária Omastová 《Journal of Polymer Science.Polymer Physics》2009,47(8):764-774
Polyamide 6 (PA6)/multi‐walled carbon nanotubes (MWCNT) nanocomposites were produced by diluting a masterbach containing 20 wt % nanotubes using melt mixing. The influence of the addition of well dispersed MWCNT (as indicated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM)) on the thermal transitions, and crystallization behavior of the PA6 matrix is investigated. Differential scanning calorimetry (DSC) results show a reduction in heat capacity jump at the glass transition which is interpreted by an immobilized interfacial layer near the nanotubes. Furthermore, both DSC and X‐ray diffraction (XRD) measurements indicate that nanotubes favor the formation of the α crystalline form of PA6. These findings are correlated with the observed improvement of the storage modulus as revealed by dynamic mechanical thermal analysis (DMTA). Additionally, a new crystallization peak appears when MWCNT are added, and is attributed to the formation of a different morphology of the same type crystallite around the nanotubes walls (trans‐crystallinity). Finally, water sorption measurements show an increase of water content, normalized to the amorphous polymer fraction, in the nanocomposites. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 764–774, 2009 相似文献
66.
V. V. Shilov V. V. Shevchenko P. Pissis A. Kyritsis Yu. P. Gomza S. D. Nesin N. S. Klimenko 《Solid State Ionics》1999,120(1-4):43-50
Thermal transitions, morphology and electric conductivity of polyurethanes that contain acid (COOH) groups bound to their polyether (poly(tetramethylene oxide)) chains and hard urethane segments of various length have been studied by means of calorimetry, wide- and small-angle X-ray scattering and a.c. conductivity in wide range of frequencies (0.1 Hz–1 MHz) and temperature (−100 to 100°C). It was shown that the polyurethanes are basically microphase-separated systems whose polyether-rich matrix contain from 20 to 25% of the hard urethane fragments. The protonic conductivity of the materials decreases with decreasing the polyether phase in the system. 相似文献
67.
Kalogeras IM Roussos M Vassilikou-Dova A Spanoudaki A Pissis P Savelyev YV Shtompel VI Robota LP 《The European physical journal. E, Soft matter》2005,18(4):467-481
Structural characteristics, thermal transitions and molecular dynamics of
selected poly(amide urethane)s with transition metal acetyl acetonates Me(AcAc)2 (Me = Sn4+, Zn2+, Cu2+, Pb2+) as chain extenders, were comparatively investigated using small- and wide-angle X-ray scattering (SAXS, WAXS), differential
scanning calorimetry (DSC), and
dielectric techniques (dielectric relaxation spectroscopy, DRS; thermally stimulated currents, TSC). We studied the influence
of metal chelates on the mixing of the soft-segment (SS) and hard-segment (HS) domains and the related degree of microphase
separation (DMS). The reactivity of Me(AcAc)2 with macrodiisocyanate was found to decrease in the order Sn(AcAc)2Cl2 > Cu(AcAc)2 > Zn(AcAc)2 > Pb(AcAc)2. While Pb(AcAc)2 shows a higher tendency for
crystallisation, both the dielectric and calorimetric results suggest that the corresponding polyurethane has comparatively
low DMS. The type of the transition metal has moderate effect on the glass transition temperature and no influence on the
shape of the dielectric α relaxation signal,
indicating weak interactions between metal ions and SS domains. In contrast, structural parameters and the dielectric behaviour
of the β relaxation suggest preference for hydrogen-bonding interactions between Sn4+ and Cu2+ metal-chelates and HS domains. The temperature dependence of dc conductivity σdc is described by the Vogel-Tammann-Fulcher equation and signifies the coupling between the mobility of polymeric chains and
charges' motion. It may be expected that the present combination of techniques and particular results with respect to DMS
will contribute to the development and testing of novel biodegradation-resistant and antibacterial metal-polyurethanes for
biotechnological and industrial applications. 相似文献
68.
Yevgen Mamunya Athanasios Kanapitsas Polycarpos Pissis Gisele Boiteux Eugene Lebedev 《Macromolecular Symposia》2003,198(1):449-460
Organic-inorganic polymer blends (OIPB) were obtained by reaction of organic and inorganic oligomers. The organic oligomer was synthesized with 2,4-toluene diisocyanate (TDI) and oligooxypropylene glycols (OPG) with various molecular weights (MW). The inorganic component was a water solution of sodium silicate. The OIPB obtained are hydrophilic and have great water sorption ability (the relative weight of sorbed water reaches 2000 %). The kinetics of water sorption and the changes of electrical conductivity during sorption were studied. Sorption ability, and mechanical, electrical and dielectric properties of OIPB depend on molecular weight of OPG: conductivity increases with increasing MW, whereas the sorption ability correlates with the mechanical properties. The influence of the inorganic phase content on the electrical and dielectric properties was studied as well. 相似文献
69.
Yevgen P. Mamunya Eleonora G. Privalko Eugene V. Lebedev Valery P. Privalko Francisco J. Balta Calleja Policarpos Pissis 《Macromolecular Symposia》2001,169(1):297-306
Metal‐filled composites of a commercial PVC (polyvinyl chloride) powder (mean particle size dp ≈ 100 microns) and a metal powder (mean particle size df about 100 microns for copper, Cu, and about 10 microns for nickel, Ni) prepared by mechanical mixing in a ball mill, subsequent hot‐pressing at 443 K and rapid cooling to 300 K, were characterized by the room‐temperature measurements of electrical conductivity σ, density ρ and microhardness H. The sudden jumps of about 17 orders of magnitude followed by a much slower growth up to the limiting filler fraction ϕ* on the log σ vs. ϕ plots are the evidence for the onset of percolation transitions, at filler volume contents ϕc1 = 0.05 and 0.04 for PVC/Cu and PVC/Ni, respectively. For both systems, the values of H exhibited an initial steep increase up to ϕc2 = 0.07, followed by an apparent plateau extending up to ϕ = 0.18. However, drastic differences in the patterns of composition dependence of H were observed at higher metal loadings, i.e., a continuous increase of H up to the leveling‐off at ϕ* for PVC/Cu, in contrast to a sudden drop of H at ϕ = 0.20 and subsequent slow increase for PVC/Ni. For both composites the apparent density ρ′ of a polymer matrix remained the same as that of the neat PVC in the composition interval ϕ < 0.20, while at ϕ* > 0.20 a precipitous drop of ρ1 was observed due to the formation of polymer‐free voids between filler particles (crowding effect) as ϕ approaches ϕ*. The observed effects were analyzed in terms of a tentative model envisaging cross‐overs from “dilute suspension regime” to “semi‐dilute suspension regime” in the concentration range ϕc1 to ϕc2, and from “semi‐dilute suspension regime” to “concentrated suspension regime” above ϕ = 0.20. Different behavior in this latter regime was explained by intrinsic differences in the structure of conductive infinite clusters between mixtures of particles of about the same size (PVC/Cu) and of widely different sizes (PVC/Ni). 相似文献