Dilute suspensions of polydisperse polystyrene microgels in the size range
of 5-50 nm in organic solvents were evaporated under controlled conditions,
and the resulting two-dimensional packing structures were investigated. Th
e particles form highly ordered structures, as revealed by electron microsc
opy. The ordering process is understood as a unique self-organization proce
ss, in which differences in the particle size and the polydispersity of the
particles are a main driving force. The structures follow the rules of hyp
erbolic geometry and are named "Zenon"-packing, indicating that the two-dim
ensional structures without translational invariance can still be understoo
d as a special form of a regular lattice. A systematic variation of the sol
vent quality and the surface tension of the suspension shows that the order
ing essentially is based upon size-dispersive van der Waals attractions bet
ween the microgels.