Self-assembly of hexagonal rod arrays based on capillary forces

A series of well-ordered, extended mesostructures has been generated from hexagonal polyurethane rods (15 x 3.2 mm) by self-assembly using capillary forces. The surface of one or more sides of the rods was rendered hydrophilic by exposure to an oxygen plasma. This modification determined the pattern of hydrophobic and hydrophilic faces; the hydrophobic sides were coated with a thin film of a hydrophobic lubricant. Agitation of the rods in an approximately isodense aqueous environment resulted in their self-assembly, in a process reflecting the action of capillary forces, into an array whose structure depends on the pattern of hydrophobic sides; capillarity also aligned the ends of the rods. We also carried out experiments in reaction chambers that restricted the motion of the rods; this restriction served to increase the size and regularity Of the assemblies. (C) 2000 Academic Press.