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These ordered arrays have a high degree of orientational order, which can be seen both from micrographs shown here and from diffraction patterns showing the hexagonal symmetry. Defects invariably form during this process and this system provides a model system for studying defect dynamics, orientational correlations across grain boundaries and in general, the two dimensional crystallization and packing. We are investigating a variety of problems that encompass nucleation and growth, droplet non-coalescence and bubble/droplet dynamics.

We report studies of ordered microporous and nanoporous polymer films formed by the evaporation of polymer solutions following exposure to a humid atmosphere. High speed microphotographic (HSMP) studies of the formation process showed that near the surface of the polymer solution, vapour condensation produced near mono-disperse water droplets which form a close-packed monolayer (or 'breath figure'). Following the evaporation of the solvent, characterisation of the solid by Atomic Force Microscopy and Scanning Electron Microscopy revealed that the surface of the polymer film is characterised by extensive regions of hexagonally close-packed microscopic pores, whose spatial arrangement replicates that of the initial droplet monolayer. Characterisation of sections of the film by Atomic Force Microscopy established that the surficial pores represent open sections of sub-surficial spheroidal cavities formed by encapsulation of the water droplets within the polymer solution. An interesting feature of the results is the occurrence of nano-scale pores at the film surface and at (and within) the walls of the sub-surficial microscopic pores. This is the first physical evidence report of such features in porous polymer films produced by a process involving breath-figures. Their dimensions suggest that more detailed structural investigations will require alternative techniques to conventional, optical methods.

SEM image of a bubble array formed from a mixture of polystyrene (65 %) and polymer 3 at ambient temperature (EHT=20.00 kV, WD=21 mm). Right: Same material, pyrolyzed at 530 °C, viewed under a conventional light microscope. All polystyrene has burned off as seen in this optical micrograph.

We describe the synthesis of two cyclobutadiene(cyclopentadienyl)cobalt-containing poly(p-phenylene ethynylene)s (PPEs) and their use as precursors for stable ceramic surface coatings. Organometallic PPEs were shaped into hexagonally ordered assemblies by using the breath-figure method. Such breath figures can be washed away with an appropriate solvent. Upon pyrolysis at 500degreesC under either nitrogen or air, the bubble arrays persist as ceramics and are insoluble in organic solvents or water. ne formed pyrolyzed bubble arrays were analyzed by optical and scanning electron microscopy, as well as energy dispersive X-ray microanalysis (EDX). The composition of the ceramic materials is discussed based on EDX and IR data.

Hexagonal bubble arrays formed by evaporation of dilute solutions of conjugated polymers in carbon disulfide.

Microstructuring of conjugated polymers is facile utilizing,the breath figure approach. Dilute solutions of conjugated polymers in carbon disulfide form highly ordered 2D hexagonal bubble arrays (see Figure and inside cover). The arrays are obtained if moist air is blown over the polymer solutions. Evaporative cooling leads to condensation of water droplets onto the liquid surface. After the solvent is evaporated, the ordered bubble array is observed.

	Sequence of images (180 x 180 micron square) depicting the growth and aggregation of water droplets near the surface of porating polymer solution. The time interval between frames #1 and #5 is 50 seconds. Ultmately, the droplets from an d-hexgonal structure as shown in frame #6.
	AFM image of the surface of a solid polymer film revealing a hexagonal arrangement of pores produced after evaporation of both solvent and water