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Rapid (0.3 s) and reversible biomimetic response of flexible dielectric mirrors was achieved by alternating inorganic (titania) and organic (poly(2-hydroxyethyl methacrylate, pHEMA) layers. Tunable reflectance bands in the visible range resulted from water swelling of the un-cross-linked pHEMA layers, without affecting the optical thickness of the high refractive index inorganic layer, which is in precise analogy to the structural color changing mechanism employed by many natural species. Larger refractive index contrast than accessible for all organic mirrors allow the desired reflectivity to be achieved with fewer layers and hence less overall thickness. The observed optical responses quantitatively match model predictions and are completely reversible. There is no loss in reflectivity intensity upon swelling. Hybrid heterostructures were grown within a single hot-wire chemical vapor deposition (CVD) chamber, resulting in smooth and uniform nanoscale layers of high interfacial quality. To the best of our knowledge, this is the first ever combination of an inorganic thin film with a fully functional polymer thin film having interfacial smoothness at the nanoscale. The room-temperature solventless HWCVD process is scalable to large area roll-to-roll deposition and is compatible with deformable substrates such as paper and plastic. [ABSTRACT FROM AUTHOR]

Degradation experiments and model studies suggested that the longer lived green fluorescence from an aggregated poly(p-phenylene ethynylene) (PPE) was due to the presence of highly emissive, low-energy, anthryl defect sites rather than the emissive conjugated polymer excimers proposed in a previous report. After elucidating the origin of the green fluorescence, additional anthryl units were purposely incorporated into the polymer to enhance the blue-to-green fluorescence color change that accompanied polymer aggregation. The improved color contrast from this anthryl-doped conjugated polymer led to the development of crude solution-state and solid-state sensors, which, upon exposure to water, exhibited a visually noticeable blue-to-green fluorescence color change. [ABSTRACT FROM AUTHOR]

Iptycene-type quinoxaline and thienopyrazine monomers were successfully synthesized via a condensation between 10-dihydro-9,10-ethanoanthracene-11,12-dione and the corresponding diamines. Copolymers based on fluorene and three iptycene monomers were prepared via Suzuki coupling reaction, and they exhibited good solubility in appropriate organic solvents. These copolymers are fluorescent in both solution and the solid state, emitting blue, greenish-blue, and red color due to the different electronic properties of the iptycene comonomers. The difference in their absorption and emission spectra was attributed to the donor−acceptor charge transfer interactions and/or polymer backbone conformational changes induced by steric effects. Moreover, the spectroscopic data clearly demonstrated the insulating effect of iptycene units, which prevented the aggregation of the polymer chains and the formation of excimers in the solid state. [ABSTRACT FROM AUTHOR]

We present a new route for the fabrication of highly nonspherical complex multivalent submicron particles. This technique exploits the ability of holographic interference lithography to control geometrical elements such as symmetry and volume fraction in 3D lattices on the submicron scale. Colloidal particles with prescribed complex concave shapes are obtained by cleaving low volume fraction connected structures fabricated by interference lithography. Controlling which Wyckoff sites in the space group of the parent structure are connected assures specific “valencies” of the particles. Two types of particles, 2D “4-valent” and 3D “6-valent” particles are fabricated via this technique. In addition to being able to control multivalent particle shape, this technique has the potential to provide tight control over size, yield, and dispersity. [ABSTRACT FROM AUTHOR]