  We present a new material which displays anisotropic and mechanical
properties tuneable during synthesis under magnetic field. It is formulated by
mixing aqueous suspensions of polymer nanolatex and magnetic nanoparticles,
coated by a thin silica layer to improve their compatibility with the polymeric
matrix, followed by casting. The magnetic properties of these nanoparticles
enable their pre-orientation in the resulting nanocomposite when cast under
magnetic field. Detailed insight on dispersion by Small Angle Neutron
Scattering (SANS) shows chainlike nanoparticle aggregates aligned by the field
on the nanometer scale. Applying strain to the nanocomposite parallel to the
particle chains shows higher mechanical reinforcement, than when strain is
transverse to field. . SANS from strained samples shows that strain parallel to
the field induce an organization of the chains while strain perpendicular to
the field destroys the chain field-induced ordering. Thus improved mechanical
reinforcement is obtained from anisotropic interconnection of nanoparticle
aggregates.
