Effect of scale and surface chemistry on the mechanical properties of carbon nanotubes‐based composites

In this article, Multi‐Walled Carbon Nanotubes (MWCNTs) of varying diameters, both untreated and polycarboxylated, were dispersed at constant weight percentage in an epoxy matrix, and resulting fracture toughnesses (K_Ic) were measured in each case. We show that changing the MWCNT diameter has two effects on the composite fracture toughness: (i) a small MWCNT diameter enables larger interfacial surface for adhesion maximization, which increases toughness; (ii) at the same time, it limits the available pull‐out energy and reduces the MWCNT ability to homogeneously disperse in the matrix due to this same large active surface: this decreases toughness. Most commercially available MWCNTs have a length range of several μm, thus an optimal diameter exists which depends on MWCNT wall thickness and surface treatment. Such optimal diameter maximizes pull‐out energy and thus composite fracture toughness. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Magnetically responsive carboxylated magnetite-polydipyrrole/polydicarbazole nanocomposites of core-shell morphology. Preparation, characterization, and use in DNA hybridization

Novel bis-heterocyclic mono- and dicarboxylated dipyrrole and dicarbazole monomers have been synthesized in a modular manner. Their oxidative polymerization around magnetite nanosized particles has been investigated and optimized toward new magnetic magnetite-polydipyrrole/polydicarbazole nanocomposites (NCs) of a core-shell morphology. These NCs were thoroughly characterized by FT-IR, TGA (Thermal Gravimetric Analysis), low- and high-resolution TEM/HR-TEM microscopies, and M?ssbauer spectroscopy along with magnetization studies. Exploiting the versatile COOH chemistry (activation by water-soluble diimides) introduced by the polymeric shell, DNA hybridization experiments have been conducted onto NC surfaces using an efficient blue-colored HRP-based enzymatic screening biological system. Highly parallel NC-supported DNA hybridization experimentations revealed that these NCs presented an interesting potential for DNA-based diagnostic applications.     

On initial,boundary conditions and viscosity coefficient control for Burgers' equation

In order to use the optimal control techniques in models of geophysical flow circulation, an application to a 1D advection–diffusion equation, the so-called Burgers' equation, is described. The aim of optimal control is to find the best parameters of the model which ensure the closest simulation to the observed values. In a more general case, the continuous problem and the corresponding discrete form are formulated. Three kinds of simulation are realized to validate the method. Optimal control processes by initial and boundary conditions require an implicit discretization scheme on the first time step and a decentered one for the non-linear advection term on boundaries. The robustness of the method is tested with a noised dataset and random values of the initial controls. The optimization process of the viscosity coefficient as a time- and space-dependent variable is more difficult. A numerical study of the model sensitivity is carried out. Finally, the numerical application of the simultaneous control by the initial conditions, the boundary conditions and the viscosity coefficient allows a possible influence between controls to be taken into account. These numerical experiments give methodological rules for applications to more complex situations. © 1998 John Wiley & Sons, Ltd.     

Multi-component hybrid inorganic–organic–inorganic particles with various metal oxide outer shells

Non-agglomerated hybrid particles of 200 nm diameter with an outer metal oxide shell were prepared by reacting the COOH groups of poly((S)-N-dicarbazolyl-lysine)-covered silica particles with metal alkoxides, such as titanium, zirconium and aluminum alkoxides, followed by sol–gel processing. With tetraethoxysilane (Si(OEt)₄), the silica particle core was growing rather than forming an external metal oxide shell, as observed for the other tested metal alkoxides.     

Novel carboxylated pyrrole- and carbazole-based monomers. Synthesis and electro-oxidation features

Carboxylated pyrrole (Pyr, a index)- and carbazole (Cbz, b index)-containing monomers 6-7a/b and 9a/b have been readily synthesized from the monobenzyl ester of L-glutamic acid and triamine 2 using Clauson-Kaas and amide coupling reactions. In contrast to Pyr-containing compounds 6-7a, and 9a, the three Cbz-containing monomers 6-7b, and 9b have been found electroactive and were successfully electropolymerized on a Pt electrode resulting in the deposition of corresponding insoluble electroconducting polyCOOH polyCbz-films poly(6-7b) and poly(9b).     

Durable bonding of silica nanoparticles to polymers by photoradiation for control of surface properties

Improvement of superhydrophobic surfaces durability is a critical key for potential commercial applications such as self‐cleaning and ice repellency. In this study, functionalization of silica nanoparticles by photoreactive benzophenone groups was made in order to covalently bond nanoparticles to polymer substrates to obtain durable coatings. Upon ultraviolet irradiation reactive excited triplet benzophenone species are formed enabling them to react with the polymer matrix through hydrogen abstraction. Two matrices were studied: radiation‐curable urethane acrylate and epoxy. The bonding of the particles to the surfaces was evaluated using atomic force microscope nanomanipulation and cross‐section analysis. The results have shown a greater stability of the photoreactive silica nanoparticles. Copyright © 2014 John Wiley & Sons, Ltd.