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Eslami H.,Ecole Polytechnique de Montreal | Grmela M.,Ecole Polytechnique de Montreal | Bousmina M.,Laval University | Bousmina M.,Hassan II Academy of Science and Technology
Journal of Rheology | Year: 2010

Linear and nonlinear (in both steady and transient shear flows) rheological properties of polymer/layered silicate nanocomposites prepared by melt mixing of poly(butylene succinate-co-adipate) and organically modified montmorillonite are investigated. Morphology of the nanocomposites is observed by x-ray diffraction and by transmission electron microscopy. Linear viscoelastic measurements in oscillatory shear with small strain amplitude show a low frequency plateau for storage modulus (an indication of a pseudo-solid like structure). A strong shear-thinning behavior for all ranges of shear rates is observed for high clay loading. An unusual behavior is observed for steady state normal stress differences. At low shear rates their values are larger than those observed for pure polymer. An inverse relation is observed at relatively high shear rates. The two models [Eslami, H., M. Grmela, and M. Bousmina, "A mesoscopic rheological model of polymer/layered silicate nanocomposites," J. Rheol. 51, 1189-1222 (2007); Eslami, H., M. Grmela, and M. Bousmina, "A mesoscopic tube model of polymer/layered silicate nanocomposites," Rheol. Acta 48, 317-331 (2009)] that we have developed previously allow us to relate the observed rheological behavior to the physics taking place in the nanocomposites on a mesoscopic level. The models take into account the chain-chain, chain-lamella, and lamella-lamella interactions. With their help, we are also able to separate contributions from the polymer and the nano charge. © 2010 The Society of Rheology. Source


Sekkat Z.,Mohammed V University | Sekkat Z.,Hassan II Academy of Science and Technology
Journal of the Optical Society of America B: Optical Physics | Year: 2010

I develop a theory that predicts a two-photon-induced molecular polar order in solid polymers at a temperature far below the glass transition temperature of the polymer. Phenomenologically, the rotational mobility of the chromophores is enhanced during a two-photon isomerization process, allowing for polar order to build up in the presence of a dc field that is applied across the solid polymer. No (or negligible) poling is possible in the absence of two-photon isomerization. Using the formalism of Legendre polynomials solves the general equations of the theory, and analytical solutions are derived for the early time evolution and the steady state of this two-photon poling process. The effects of the poling parameters are discussed, and it is shown that the twophoton poling efficiency can be as high as that achieved by dc field poling at elevated temperatures. © 2009 Optical Society of America. Source


Nesterenko D.V.,Innovation and Research MAScIR | Sekkat Z.,Innovation and Research MAScIR | Sekkat Z.,Mohammed V University | Sekkat Z.,Hassan II Academy of Science and Technology
Plasmonics | Year: 2013

Figures of merit are introduced for estimation of achievable resolution of surface plasmon (SP) sensors by modulation type. The resolution of SP sensors in the Kretschmann's geometry is estimated by numerical simulation for combinations of silver (Ag), copper (Cu), aluminum (Al), chromium, and titanium layers with a gold (Au) layer in the ultraviolet (UV), visible, and infrared (IR) regions in cases of detecting the change of the refractive index of water and the presence of an adsorption layer in water. SP biosensors with angular modulation based on Al exhibit low resolution in the UV region; Ag, Au, and Cu biosensors show best resolution in the visible region. Biosensors with intensity modulation demonstrate high performance in the near IR by Ag, Au, and Cu metals, and in the UV by Al. © 2013 Springer Science+Business Media New York. Source


Sekkat Z.,Optics and Photonics Center | Sekkat Z.,Mohammed V University | Sekkat Z.,Hassan II Academy of Science and Technology | Kawata S.,Osaka University | Kawata S.,RIKEN
Laser and Photonics Reviews | Year: 2014

Recent progress in the field of single- and two-photon nanofabrication, both 2- and 3-dimensional, in photopolymerizable resins and in films of photoisomerizable azopolymers are reviewed. The basic processes as well as technological advances and applications of nanofabrication by light are discussed. Recent advances and achievements in polymer photomechanics and light-activated molecular movement in azopolymers are also reviewed. Recent progress in the field of single- and two-photon nanofabrication, both 2- and 3-dimensional, in photopolymerizable resins and in films of photoisomerizable azopolymers are reviewed. The basic processes as well as technological advances and applications of nanofabrication by light are discussed. Recent advances and achievements in polymer photomechanics and light-activated molecular movement in azopolymers are also reviewed. © 2013 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Lamnawar K.,University of Lyon | Bousmina M.,Hassan II Academy of Science and Technology | Maazouz A.,University of Lyon | Maazouz A.,Hassan II Academy of Science and Technology | Maazouz A.,CNRS Laboratory for Polymer Materials Engineering
Macromolecules | Year: 2012

The aim of the present work has been to gain a fundamental understanding of the mechanisms governing encapsulation in the multiphase systems as a blend or multilayer structures. The model systems chosen for this study are based on (i) Newtonian poly(dimethylsiloxane) polymers of varying molar masses and (ii) high molecular weight, viscoelastic, and compatible pair polymers of PVDF and PMMA. The same approach was applied to functionalized polymers to investigate the effect of physicochemical affinity on two pairs of asymmetrical reactive polymers based on PE-GMA (glycidyl methacrylate)/PVDF-g-MA (maleic anhydride) and a PE/PVDF as a reference. The linear viscoelastic and surface properties of the neat and bilayer model systems structures have been investigated. The optical obeservations of the encapsulation kinetic of two drops were recorded using a homemade device. Specific experiments were carried out to follow up the kinetic of encapsulation, and the results were rationalized as a function of the effect of the viscosity, elasticity ratios, drop geometry, the interfacial tension, and the physicochemical affinity. Throughout all the experiment, the mechanisms were purposed for each system and discussed based on the theories of molecular forces or Brownian motion governing diffusion and Ostwald ripening, in contrast to the theories of coalescence. The viscosity ratio coupled to the drop geometry of the material was found to be a key parameter and that it has to be linked to the interfacial tension and spreading parameters. Furthermore, the encapsulation appeared to be hindered by the interdiffusion process in the case of compatible pair system despite their elasticity and surface tension contrast. Finally, the encapsulation kinetic could be reduced or eliminated by the creation of a copolymer at the interface for a reactive system. The results obtained by the optical investigation of two drops corroborated the rheological data of the bilayer systems. Hence, the obtained results rendered it possible to decouple the influence of the viscoelastic parameters to flow, interfacial tension, thereby highlighting a number of macroscopic effects that were governed by the interdiffusion or reaction of macromolecular chains at the interface to give a better understanding of encapsulation phenomenon in multiphase systems. © 2011 American Chemical Society. Source

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