Electrically conductive PTT-block-PTMO/SWCNTs+Graphene Nanoplatelets hybrid nanocomposites prepared by in situ polymerization

Hybrid Materials 2015; Sitges, Barcelona, Spain, 9 - 13 March 2015The studies were financed by the National Science Centre within project PRELUDE no 2013/11/N/ST8/00404.Peer Reviewe

Broadband dielectric spectroscopy of nanocomposites based on PVDF and expended graphite

2nd International Conference on Structural Nano Composites (NANOSTRUC 2014); 6 pags.; 4 figs.; Open Access funded by Creative Commons Attribution 3.0 licence.Nanocomposites based on poly (vinylidene fluoride) (PVDF) and expanded graphite (EG) were prepared by non-solvent precipitation from solution with different EG concentrations. Films were obtained by compression molding and their structural and dielectric properties studied. From Wide Angle X-ray Scattering (WAXS) experiments, it can be assessed that for all EG concentrations the -crystalline phase of PVDF is the predominant crystalline form. However, for composites with high nanoadditive content, higher than 3 wt.%, the -crystalline phase is also detected. Dielectric spectroscopy results showed that the nanocomposites present both high dielectric constant and electrical conductivity at low percolation threshold. Published under licence by IOP Publishing LtdThe authors thank the financial support from the Spanish Ministry of Science and Innovation (MICINN), Grant MAT2012-33517 and from the Polish National Science Centre and the Slovak Academy of Sciences in the frame of ERA-NET project APGRAPHEL.Peer Reviewe

Temperature dependence of the FMR absorption lines in viscoelastic magnetic materials

The magnetic properties of the viscoelastic materials filled with magnetic nanoparticles strongly depend on the viscosity of these materials. The time-temperature changes of the viscosity can affect the orientation ordering of the anisotropy axes of the magnetic nanoparticles after an external magnetic field is applied. In consequence, the absorption lines obtained in the ferromagnetic resonance experiment (FMR) will possess an additional temperature dependence through the viscosity of the materials under consideration. The particular case of the temperature dependence of the FMR signal detected from the γ-Fe2O3 (maghemite) magnetic nanoparticles dispersed at low concentration (0.1 wt.%) in a poly(ether-ester) multiblock copolymer (PEN-block-PTMO)) matrix has been investigated. A strong increase of the resonance line amplitude is observed with increasing temperature. We note also two qualitatively different temperature dependences of the magnetic resonance field at low and high temperatures. A simplified theoretical model of a single cluster consisting of N magnetic nanoparticles in an elastic polymer matrix is introduced to explain these temperature dependences of the absorption lines. The model is based on the stochastic version of the Lifshitz-Landau equation for nanoparticle magnetization. © 2010 Elsevier B.V. All rights reserved

The influence of soft segment length on structure and properties of poly(trimethylene terephthalate)-block-poly(tetramethylene oxide) segmented random copolymers

Two series of multiblock poly(ether-ester)s based on poly(trimethylene terephthalate) (PTT) as the rigid segments and poly(tetramethylene oxide) (PTMO) as the flexible/soft segments were synthesized with the aim of developing of the new family polyester thermoplastic elastomers (TPEs) based on PTT as rigid segment. The content of PTMO segments in the polymer chains was varied from 20 to 80 wt%. The investigations were mainly focused on the influence of flexible segments length with starting PTMG molecular weight at 1000 and 2000 g/mol, respectively, on the phase structure, thermal and mechanical properties of resulting copolymers. The copolymers were characterized by Size Exclusion Chromatography (SEC), Differential Scanning Calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), Wide-angle X-ray scattering (WAXS), Small-angle X-ray scattering (SAXS), and other standard physical methods. Cyclic tensile properties of them were studied with the aim to evaluate the elastic properties. SEC results clearly demonstrated the formation of molecular weight segmented copolymers with microphase separated structure as denoted by DSC and DMTA. The enhanced phase separation was observed for copolymers containing longer flexible segments.According to the characterizations, copolymers containing 50-80 wt% of flexible segments showed elastic behavior. Comparison of the values of permanent set for copolymers with shorter and longer flexible segments has shown that copolymers containing 30 and 40 wt% of long PTMO flexible segments have the best elastic properties (low permanent set)