Abstract
Scientific interest in dynamic interactive systems with engineered interactions on extended scales is continuously growing because these systems may display novel properties not present at the molecular level.1–3 Understanding and controlling the scale-up from the molecular level toward nanoscale dimensions4–6 might provide new insights into basic features in the design of emergent systems at the heart of modern technologies such as tissue engineering,7 artificial organs,8 catalysis,9 membrane filtration,10 and sensing.11 The de novo design of porous systems used as mechanical supports, molecular capacitors/distributors, or gating effectors and the use of strategies based on self-healing,12–14 self-cleaning,15, 16 and stimuli-response17 properties has become an area of growing interest. Classical membranes for water filtration are subjected to strong compression depending on their structural behavior and bulk porosity.18, 19 Irreversible compaction is usually effected in order to reach a steady-state flux, giving the membrane a stable pore size. In contrast, a responsive membrane can self-regulate its performance according to changes in environmental conditions such as pH, temperature, light, and ionic strength.20–22 In the present work, the ABA triblock copolymer poly(styrene-co-acrylonitrile)-b-poly(ethylene oxide)-b-poly(styrene-co-acrylonitrile) (PSAN-b-PEO-b-PSAN) has been used to generate flowerlike micelles. They consist of a compressible hydrophilic soft corona of PEO (26 vol %) and a hydrophobic hard core of PSAN which maintains the micelle’s structural integrity (Figure 1). When a copolymer solution is spin-coated onto a silicon wafer, evaporation of the solvent results in the formation of a porous film through the assembly of micelles 50 nm in diameter. Reversible noncovalent interactions between the micelles mediate their dynamic self-assembly at the macroscopic level such that there is free volume between the micelles, imparting nanoporosity to the film.23–27