A novel fabrication process is presented using monodisperse PMMA latex particles to facilitate controlled microvoid formation. This results in hierarchically rough surfaces exhibiting ∼90% optical transmission while retaining water contact angle (θ) of 170°. Synchrotron small angle X-ray scattering, AFM roughness measurements, and theoretical modeling suggests that a surface morphology with fractal dimension of ∼2.6 and R a < 400 nm allows for the optimum coupling of roughness-induced superhydrophobicity and optical transparency. Interestingly, surfaces of vastly different roughness (R rms) exhibited similar water contact angles, highlighting a limitation of traditional AFM roughness measurements in quantifying multiscale rough surfaces. An alternate method considering fractal dimension is presented as a more complete quantifier of hierarchical surface morphology in relation to surface wetting behavior.

Single crystal X-ray, NEXAFS and OFET studies on angular polycyclic aromatic silyl-capped 7,14bis(ethynyl)dibenzo[b,def]chrysenes.

The current study reports the fabrication and characterization of superhydrophobic surfaces with increasing nanoroughness by decreasing silica nanoparticle size in a sol–gel matrix. Using small-angle X-ray scattering (SAXS) measurements allowed for the direct quantification of air entrapped at the interface, revealing for the first time that significant air remains on hierarchical surfaces despite observed droplet pinning through hysteresis measurements. Combining contact angle hysteresis and SAXS measurements of the surfaces immersed in sodium dodecylsulfate (SDS) solutions with Cassie and Tadmor’s model, a series of predicted contact angles were generated, comparing wetting transition mechanisms based on wetting line advance, droplet adhesion/pinning, and interfacial air entrapment. The study provided confirmation of key theoretical assumptions on wetting of hierarchical surfaces: (i) Cassie wetting of the nanofeatures is the preferred wetting progression on hierarchical surfaces; and (ii) the presence of an intermediate petal state is dependent on the level of nanoroughness as compared to the microroughness.

A new class of self-assembling hexa-peri-hexbenzocoronene (HBC)-fullerene hybrid materials has been synthesized and characterized. Photoluminescence experiments indicate that energy transfer processes can be tuned in these donor-acceptor systems by varying the length and nature of the linker group. In preliminary device testing, ambipolar charge transport behavior is observed in organic field effect transistors, while single active component organic photovoltaic devices consisting of these materials achieved a maximum external quantum efficiency of 30%.