Morphology and wettability control of honeycomb porous films of amphiphilic fluorinated pentablock copolymers via breath figure method

Abstract

Amphiphilic pentablock copolymers of poly (trifluoroethyl methacrylate)-b-poly (methyl methacrylate)-b-poly (ethylene glycol)-b-poly (methyl methacrylate)-b-poly (trifluoroethyl methacrylate) (PTFEMA-b-PMMA-b-PEG-b-PMMA-b-PTFEMA) with three different block ratios as well as molecular weights were used to fabricate honeycomb structured porous films through the breath figure technique. Several critical influencing factors such as macromolecular structures, solvent properties, copolymer concentrations and the substrates were investigated to control the morphology of the pores. The results showed that chloroform utilized as a solvent with an appropriate concentration of 45 mg mL⁻¹ on the substrate of silicon wafer offered the optimum condition. It could be evidenced that the pore sizes of the honeycomb films were increased by enhancing the molecular weight of the copolymer. In addition, an increase in the copolymer concentration leads to a decrease in the pore size, and even causes a few porous structures to disappear. The viscosity of the liquid substrates also affects the pore size, and it was found that a larger pore size was formed with an increase in the viscosity. The porous films possessed better hydrophobic and oleophobic properties than the flat films. In addition, the pincushion structure films exhibited the best hydrophobic and oleophobic properties and an excellent water-adhesion ability in the reverse state. This work may facilitate our understanding of the breath figure process and assist us in preparing films under different conditions, which show different perspectives as micro-suckers, hydrophobic and oleophobic membranes.