Porous polymer film formation by water droplet templating using polystyrene.

Studies show that the formation of breath figures over polystyrene is not clearly understood-sometimes the patterns are regular and sometimes they are barely formed. In an attempt to understand this process a little more, breath figures over polystyrene of three molecular weights and on the smooth and grooved DVD surfaces are prepared and studied. The microporous films are prepared by the evaporation of the chloroform solution of the polymers in a humid environment. The thus formed breath figure patterns are studied under a confocal laser scanning microscope and the images are analyzed. Breath figures were formed for (a) three molecular weights of the polymer (b) two casting techniques, and (c) on smooth and grooved surfaces (of a commercial DVD). The wetting of the breath figures formed by water is also reported here. The pore diameters were found to increase with increase in molecular weight and also with concentration of the polymer used. Only drop-casting method yield breath figures. Voronoi entropy, calculated from the images, indicates ordered pores on the grooved surface compared to smooth surfaces. Contact angle studies indicate a hydrophobic nature of the polymer, with the hydrophobicity increasing by the patterning.