Srinivasrao et al (Science, 292 (5514): 79 APR 6 2001) reported the formation of a three dimensionally ordered array of air bubbles of monodisperse pore size in a polymer film through a templating mechanism unlike most published in the literature. Dilute solutions of a simple, coil-like polymer in a volatile solvent are cast on a glass slide in the presence of moist air flowing across the surface. Evaporative cooling, and the generation of an ordered array of breath figures, forms multilayers of hexagonally packed water droplets that are preserved in the final, solid polymer film as spherical air bubbles. The dimensions of these bubbles can be simply controlled by changing the velocity of the airflow across the surface. Such three dimensionally ordered macroporous materials with dimensions comparable to visible light are predicted to have unique optical properties such as photonic band-gaps, and optical stop-bands.

The ordered array is imaged by using three dimensional image reconstruction using the confocal microscope. The 3D structure can be obtained in conducting polymers by using dilute solutions of conjugated polymers in just a matter of few minutes. Lulu "Bubble" Song creates bubbles in a variety of polymers, and is investigating various aspects and applications of these macroporous structures





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.





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


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 ”ĘC, 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.


Releated articles

1. Srinivasarao, M; Collings, D; Philips, A; Patel, S. 2001. Three-dimensionally ordered array of air bubbles in a polymer film. SCIENCE 292 (5514): 79-83

2. Song, L; Bly, RK; Wilson, JN; Bakbak, S; Park, JO; Srinivasarao, M; Bunz, UHF. 2004. Facile microstructuring of organic semiconducting polymers by the breath figure method: Hexagonally ordered bubble arrays in rigid-rod polymers. ADVANCED MATERIALS 16 (2): 115

3. Erdogan, B; Song, LL; Wilson, JN; Park, JO; Srinivasarao, M; Bunz, UHF. 2004. Permanent bubble arrays from a cross-linked poly(para-phenyleneethynylene): Picoliter holes without microfabrication. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126 (12): 3678-3679

4. Barrow, MS; Jones, RL; Park, JO; Srinivasarao, M; Williams, PR; Wright, CJ. 2004. Physical characterisation of microporous and nanoporous polymer films by atomic force microscopy, scanning electron microscopy and high speed video microphotography. SPECTROSCOPY-AN INTERNATIONAL JOURNAL 18 (4): 577-585

5. Englert, BC; Scholz, S; Leech, PJ; Srinivasarao, M; Bunz, UHF. 2005. Templated ceramic microstructures by using the breath-figure method. CHEMISTRY-A EUROPEAN JOURNAL 11 (3): 995-1000

6. Barrow, MS; Jones, RL; Park, JO; Wright, CJ; Williams, PR; Srinivasarao, M. 2008. Studies of the formation of microporous polymer films in "breath figure" condensation processes. MODERN PHYSICS LETTERS B 22 (21): 1989-1996