Rachel Yerushalmi-Rozen

Self-assembly of nanoparticles (NPs) into nonclose-packed (ncp), semi-two-dimensional (2D) arrays is of interest in a variety of applications. Of special interest are photochemically active surfactant-like fullerene derivatives [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). The study presented here characterizes the morphology and structure of patterns formed by a mixture of PCBM NP and an amphiphilic block-copolymer tethered at the water-air interface (a surface brush) as a function of the concentration of poly(ethylene oxide) (PEO) dissolved in the liquid subphase. Theoretical modeling of the system shows that the concentration of PEO in the subphase mediates the dimensions of the surface brush and at high PEO concentrations induces a collapse of the brush at the solution-air interface. The state of the surface brush is suggested to tune the semi-2D patterns observed in the experiments via lateral depletion interactions and, in particular, induce lateral phase separation of the PCBM-block copolymer.