title: Tuning the pore composition by two simultaneous interfacial self-assembly processes: breath figures and coffee stain.
abstract: In the current paper, we prepared microstructured porous films by the breath figures approach using polymer blends consisting of polystyrene as the major component and an amphiphilic additive, either a synthetic block copolymer {two different polystyrene-b-poly[poly(ethylene glycol) methyl ether methacrylate] copolymers} or a series of commercial surfactants. Tetrahydrofuran was employed as the solvent. Confocal micro-Raman spectroscopy demonstrated the preferential location of the amphiphilic additives in the cavities of the film as a consequence of the breath figures mechanism. However, the distribution of the copolymer within the cavities varies depending upon the structure and, more precisely, the surface properties of the additives, leading to three different situations. First of all, the copolymer with a larger polystyrene segment, insoluble in the condensed water droplets, is homogeneously distributed along the whole surface of the cavities. On the contrary, when the copolymer is soluble in water (shorter polystyrene segment), it migrates inside the droplet and a coffee-stain phenomenon takes place during the water droplet evaporation, conducting to a ring-like deposition on the top edge of the cavities. Finally, when a water-soluble surfactant with high surface activity is used, the surfactant is solubilized inside the water droplets, which provokes a decrease on the surface tension and the coffee-ring effect is modified. In this situation, the copolymer covers the bottom of the pore.
authors.affiliation: Instituto de Ciencia y Tecnología de Polímeros (ICTP), Consejo Superior de Investigaciones Científicas (CSIC) , C/Juan de la Cierva 3, 28006 Madrid, Spain.
authors.forename: Alberto S
authors.initials: AS
authors.lastname: de León
authors.forename: Adolfo
authors.initials: A
authors.lastname: del Campo
authors.forename: Marta
authors.initials: M
authors.lastname: Fernández-García
authors.forename: Juan
authors.initials: J
authors.lastname: Rodríguez-Hernández
authors.forename: Alexandra
authors.initials: A
authors.lastname: Muñoz-Bonilla
mesh_terms: D005663:Furans / Q000737:chemistry; D008027:Light; D046911:Macromolecular Substances; D008422:Materials Testing; D008823:Micelles; D008853:Microscopy; D055095:Optics and Photonics; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry; D012542:Scattering, Radiation; D012995:Solubility; D013059:Spectrum Analysis, Raman; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D005663:Furans; D046911:Macromolecular Substances; D008823:Micelles; D011108:Polymers; D011137:Polystyrenes; D013501:Surface-Active Agents; D014867:Water; C018674:tetrahydrofuran