Hierarchically structured multifunctional porous interfaces through water templated self-assembly of ternary systems

Herein, a facile water-assisted templating approach, the so-called breath figures method, has been employed to prepare multifunctional and hierarchically structured porous patterned films with order at different length scales (nano- and micrometer). Tetrahydrofuran solutions of ternary blends consisting on high molecular weight polystyrene, an amphiphilic block copolymer, polystyrene-b-poly[poly(ethylene glycol) methyl ether methacrylate] (PS(40)-b-P(PEGMA300)(48)), and a fluorinated copolymer, polystyrene-b-poly(2,3,4,5,6-pentafluorostyrene) (P5FS(21)-b-PS(31)), have been used to obtain films varying the proportion of the three components. Confocal micro-Raman spectroscopy and atomic force microscopy demonstrated the preferential location of the different functionalities in the films. Because of the breath figures mechanism, the amphiphilic copolymer yield pores enriched in hydrophilic functionality while the fluorinated copolymer remained mixed with the PS matrix and eventually also forming self-assembled nanostructures at the surface. As a consequence, two levels of order can be observed, i.e., micrometer size pores with nanostructured domains due to the block copolymer self-assembly. In addition, the distribution of the amphiphilic copolymer within the holes is not regular being located principally on the edges of the cavities. This can be attributed to the coffee stain phenomenon occurring in the water droplets as a consequence of the segregation of the block copolymers to the droplets and their self-assembly.