ABSTRACT:We have studied the adsorption of end-attaching block copolymer chains inside the cylindrical pores of nanoporous alumina. Highly asymmetric PS-PEO block copolymers, with a small PEO anchoring block and a long PS dangling block, were allowed to adsorb onto porous alumina substrates with an average pore diameter of $200 nm from toluene solution. The adsorption process was monitored using FTIR spectroscopy, whereas depth profile analysis was performed by means of XPS and Ar þ ion sputtering. It is found that the PS-PEO adsorption kinetics in porous alumina are $4 orders of magnitude slower than the corresponding case of a flat alumina substrate. It appears that chains adsorbed near the pore entrance early on tend to form a barrier for chains entering the pore at later times, thereby slowing down the adsorption process significantly. This effect is much more pronounced for large chains whose dimensions are comparable with the pore diameter. The equilibrium adsorbance value is also affected by chain size due to the additional entropic penalty associated with chain confinement, the adsorbance falling substantially when the chain dimensions become comparable with the pore diameter. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48:

There is a great deal of interest in functional materials containing magnetite (Fe 3 O 4 ) due to their several advanced applications (e.g. lithium-ion batteries, wastewater treatment and drug delivery) of these materials. Recently, the ability of magnetic composite materials to operate as reliable strain sensors has attracted particular attention because of their unique mechanical and magnetic properties. Polyester polymer composites reinforced with magnetite Fe 3 O 4 micro-and nano-particles have been prepared at different particle loading levels, presenting magnetic properties. Nanoindentation technique is performed in order to study the local mechanical behavior of composites, taking into account stiffness correction after the creep deformation stage. In order to evaluate the effect of Fe 3 O 4 particles on bulk mechanical response, dynamic mechanical thermal analysis (DMTA) is used. The glass transition temperature (T g ) of the polyester filled with nanoparticles has shifted to higher temperature, as shown from the DMTA, in comparison with the composites filled with microparticles. The low concentration of particles in the micro-composites displayed enhanced reduced modulus, hardness and shear storage modulus, compared with that of pure polyester and nano-composites. Magnetic flux density-strain experiments confirmed the good strain sensitivity of the above materials.

Magnetic polymer composites were synthesized via suspension polymerization method, incorporating nanoFe3O4powder into poly (methyl methacrylate) (PMMA) and polystyrene (PS) matrices in order to obtain polymer magnetic microspheres with perspectives in sensing applications. The monomer (MMA or Styrene) and the magnetic powder (pre-made Fe3O4, 20nm in diameter) are mixed together under vigorous stirring and follows suspension polymerization. The product was sequentially filtered through a range of sieves and spherical composites were obtained with grains of sizes ranging from 45μm to 250μm. The yield of polymerization was 60% to 85% for the two different matrices in samples and the corresponding polymer product contained 1.25wt% to 4.00wt% of Fe3O4. It is observed that increasing the content of magnetite affect the surface morphology of the microspheres and their magnetic behavior. The pure nanoFe3O4powder and the magnetic polymer microspheres were characterized using techniques such as X-Ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), optical microscopy and magnetization measurements carried out by a Vibrating Sample Magnetometer (VSM) .

The aim of this work is to investigate the strain sensing properties of polyester/magnetite composite materials of different contents 5, 10, 15, 20% w/w. Specifically, we manufactured magnetic composite materials with a polyester matrix (thermosetting polymer) and nanoparticles of magnetite (Fe3O4) as additives, processed by molding technique. For these composites we used two different magnetite powders of grain sizes a) 20-30nm (premade from Alfa Aesar) and b) <1 μm (powder made by the co-precipitation method in our laboratory). The specimens were subjected into tensile stress in order to observe the alternation of Reluctance induced by strain. The sensing probe is consisted of an electromagnet and a Hall sensor (magnetic flux density sensor). The electromagnets coil is supplied by direct current (DC) causing magnetic flux to circulate the core of the specimen. The results from the tensile stress experiments show that the magnetic flux density B decreases analogous to the Strain.

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