**SESANS
DETECTS COLLOIDAL JAMMING IN NANOCONFINEMENTS **

__Rana
Ashkar__ and Roger Pynn

The
assembly of matter in nano-confinements is emerging as a low-cost candidate for
fabricating controlled highly-ordered nanomaterials. To understand this
behavior a 3D structural characterization of the confined matter is necessary. On
one hand, nondestructive probing of such samples challenges conventional
microscopy techniques. On the other hand, the submicron size of a single
confinement is impractical for neutron and x-ray scattering experiments but this
dilemma can be overcome by using a confining matrix made up of an array of
identical confinements such as the channels of a diffraction grating. The
caveat is that the periodicity of the matrix amplifies dynamical scattering
effects that are not accounted for in approximate scattering theories and a full
dynamical theory (DT) calculation becomes unavoidable. A dynamical theory model
we have recently developed gives good account of spin-echo small angle neutron scattering
(SESANS) data on nanostructured gratings. Unlike traditional diffraction
techniques that require collecting a large number of diffraction orders to
deduce the structure of materials, SESANS overcomes this problem by measuring
density correlations in *real *space. In addition, the technique allows
neutron scattering to access the length scales of interest which lie in the
few-tens-of-nanometers to several-micron range. The combination of SESANS
measurements and DT calculations on a semi dilute silica suspension in contact
with a nanopatterned grating shows jamming of the colloidal particles in the
grating channels.