Microstructural Aspects of Particle-Assisted Breath Figures in Polystyrene-Alumina Hybrid Free Standing Film

Polystyrene-alumina hybrid free standing films with amino-functionalized breath figure (BF) cavities were fabricated from a suspension of the amino-functionalized amphiphilic-modified alumina particles in polystyrene/chloroform solution by employing a one-step casting process. The role of the film thickness and the particle concentration on the BF microstructural aspects such as the pore size, pore density, amino group surface density, etc. was reported. The dry film thickness increased from 0.91 to 5.6 mu m on increasing the wet film thickness from 0.2 to 1 mm. The pore size increased with the film thickness, while the pore density and the porosity decreased. Relatively uniform pore size was observed for an similar to 3 mu m thick film in which the moderately ordered BF pattern was more or less maintained up to a particle concentration of 5 wt % of the polystyrene content. While the 0.91 mu m thick film exhibited through-pore structure, concavities were formed in thicker films. The particle-assisted BF formation favored the formation of amino-functionalized cavities. The surface density of the amino functionality reduced on increasing the film thickness, whereas the density increased with the particle concentration. The implications were discussed.