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Polymer nanoparticles of 40-400 nm diameter with spiropyran-merocyanine dyes incorporated into their hydrophobic cavities have been prepared; in contrast to their virtually nonfluorescent character in most environments, the merocyanine forms of the encapsulated dyes are highly fluorescent. Spiro-mero photoisomerization is reversible, allowing the fluorescence to be switched "on" and "off" by alternating UV and visible light. Immobilizing the dye inside hydrophobic pockets of nanoparticles also improves its photostability, rendering it more resistant than the same dyes in solution to fatigue effects arising from photochemical switching. The photophysical characteristics of the encapsulated fluorophores differ dramatically from those of the same species in solution, making nanoparticle-protected hydrophobic fluorophores attractive materials for potential applications such as optical data storage and switching and biological fluorescent labeling. To evaluate the potential for biological tagging, these optically addressable nanoparticles have been delivered into living cells and imaged with a liquid nitrogen-cooled CCD. [ABSTRACT FROM AUTHOR]

The synthesis of poly(hydridocarbyne), one of a class of carbon-based random network polymers and a structural isomer of polyacetlyene, is reported. The network backbone of this polymer is primarily composed of tetrahedrally hybridized carbon atoms, each bearing one hydride substituent and linked via three carbon-carbon single bonds into a three-dimensional random network of fused rings. This atomic-level carbon network backbone confers unusual properties on the polymer, including facile thermal decomposition to form diamond or diamond-like carbon high-quality films at atmospheric pressure, by direct deposition or by chemical vapor deposition (CVD), without the use of hydrogen or any other reagent. [ABSTRACT FROM AUTHOR]