Nanocomposite Materials with Controlled Anisotropic Reinforcement Triggered by Magnetic Self-Assembly

Abstract

Nanocomposite materials filled with nanoparticles currently exhibit two important unsolved experimental challenges: (i) the elaboration of a general strategy allowing to finely tune, for an easy-to-tune range of parameters, the anisotropy of nanoparticle assembly inside a polymer matrix for improved anisotropic mechanical reinforcement and (ii) an experimental demonstration establishing that the macroscopic mechanical properties of the materials are quantitatively controlled by the filler microstructure. We address them both here by showing how the versatile bottom-up organization of spherical magnetic nanoparticles controlled by a moderate external magnetic field during processing, enables to obtain a wide variety of anisotropic structures, from quasi-isotropic up to a homogeneous dispersion of aligned chains of nanoparticles, as shown by a refined structural study combining SAXS and TEM experiments. The resulting anisotropy of the mechanical properties is spectacular relative to the low particle volume fraction. The Young modulus can be more than 3 times higher when the bulk material is stretched parallel as opposed to perpendicular to the chains and correlates quantitatively in a proportional manner with the anisotropy of the microstructure.

Optimization of the magnetic properties of aligned Co nanowires/polymer composites for the fabrication of permanent magnets

“…Nanocomposite films with aligned nanowires formed by nanoparticles are obtained. Similar results were obtained by Robbes et al (2011). Park et al (2007 have investigated the micromechanical properties of Ni nanowire/polymer composites.…”

Perspective: Outstanding theoretical questions in polymer-nanoparticle hybrids

“…[251][252][253][254][255][256] However, to our knowledge, only a few works have considered the corresponding phenomena when magnetic NPs are placed in a polymer matrix in an external field. 25,[257][258][259] Jestin et al, for example, incorporated iron oxide NPs in a polymer matrix in the presence of solvent (Fig. 9).…”

Hairy nanoparticle assemblies as one-component functional polymer nanocomposites: opportunities and challenges

“…[1][2][3][4][5] These properties have been found to be very strongly dependent on the dispersion characteristics of nanoparticles in the polymeric matrix, [4][5][6][7] thus bringing the issue of structure control to the forefront. While this structure control can be achieved by carefully controlled processing techniques (such as blending conditions, [8] or external stimuli such as magnetic and electrical fields during synthesis) [7] scalability and reliability would be greatly improved if the desired structure and dispersion were intrinsically stable properties of the material itself.…”

“…[1][2][3][4][5] These properties have been found to be very strongly dependent on the dispersion characteristics of nanoparticles in the polymeric matrix, [4][5][6][7] thus bringing the issue of structure control to the forefront. While this structure control can be achieved by carefully controlled processing techniques (such as blending conditions, [8] or external stimuli such as magnetic and electrical fields during synthesis) [7] scalability and reliability would be greatly improved if the desired structure and dispersion were intrinsically stable properties of the material itself. The use of polymeric shells grafted to nanoparticles, originally as a method of colloidal stabilization (van der Waarden reported the use of grafted polymers to stabilize colloids as early as 1950) [9][10][11] is now widely exploited to enhance dispersion and mixing of the particles into an organic solvent or matrix by creating a compatibilizing layer between the inorganic nanoparticles and the organic matrix.…”