Investigation of super-hydrophobic effect of PMMA layers with different fillers deposited on glass support

The advancing and receding contact angles of water were measured on PMMA/filler films (0.25 cm(3)) deposited on glass surface by the spincoating method. As the fillers were used glass spheres hollows (11.3 mu m), SiO2.xH(2)O (728 nm), Al2O3, 150 neutral (2.53 mu m); polypropylene (PP) (100 nm), TiO2, P25 (135 nm), and PTFE (992 nm). They were dispersed in PMMA solution in chloroform and different content of them were used (0.066-0.2g/cm(3)). First the filler-free films of PMMA were tested to find an optimal content of PMMA in chloroform (0.1-0.6 cg/100 cm(3)). The films were produced by deposition 0.25 cm(3) of the solutions on glass surface from a syringe. The highest advancing water contact angle was measured on 0.1 g/100 cm(3) PMMA film, while the lowest on the film 0.6 g/ 100 cm(3). Using the advancing and receding contact angles (the contact angle hysteresis), the apparent surface free energy was calculated for the tested films. The former possessed lower energy than solid PMMA surface, while the latter significantly higher. AFM images showed that the thinner PMMA film possessed much more small holes in its Structure than the thicker one. Probably effect of the holes presence was similar like the presence of protrusions on a rough surface. For preparation of the PMMA/filler films, the PMMA solution of 0.1 g/100 cm(3) was used. The filler particles dispersion in the film was observed using a polarizing microscope. It was found that TiO2 and Al2O3 caused an increased wetting of the film surface, while PP presence caused super-hydrophobic effect in comparison to the reference filler-free film. The apparent contact angles on these films were around 140 independently of the PP content. Hence, the calculated apparent surface free energies were low, 5-8 mJ/m(2) only. Also silica-gel filler caused significantly increased hydrophobicity of the surface, although on these films the contact angles were only 100-130. (c) 2006 Elsevier B.V. All rights reserved.