No abstract

We report the formation of breath-figure (BF) patterns with amino-functionalized cavities in a BF incompatible polystyrene (PS) by incorporating functionalized alumina nanoparticles. The particles were amphiphilic-modified and the modifier ratio was regulated to achieve a specific hydrophobic/hydrophilic balance of the particles. The influence of the physical and chemical properties of the particles like particle concentration, the hydrophobic/hydrophilic balance, etc., on particle dispersion in solvents having different polarity and the corresponding changes in the BF patterns have been studied. The amphiphilic-modified alumina particles could successfully assist the BF mechanism, generating uniform patterns in polystyrene films with the cavity walls decorated with the functionalized alumina particles, even from water-miscible solvents like THF. The possibility of fabricating free-standing micropatterned films by casting and drying the suspension under ambient conditions was also demonstrated. The present method opens up a simple route for producing functionalized BF cavities, which can be post-modified by a chemical route for various biological applications.

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 μm 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 ∼3 μm 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 μm 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.