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During the formation of organic-inorganic hybrid materials by the sol-gel process, the observation of multiphase systems at different stages of the reaction is not uncommon. An assessment of the chemical species formed before and after gelation is not an easy task because complex mixtures are generally found in these systems. In this study, the identification of intermediates developed during the formation of a hybrid obtained from tetraethoxysilane (TEOS) and 4-[(5-dichloromethylsilyl)pentyloxy]cyanobenzene monomer has been undertaken. Solution and solid-state 29 Si-and 13 C-NMR spectra, recorded at different degrees of conversion, allow the elucidation of the mechanism of hybrid formation. 4-[(5-dichloromethylsilyl)pentyloxy]cyanobenzene, (DCN), DCN-TEOS cyclosiloxanes and low-molecularweight linear copolysiloxanes are formed in the early stages of the process and before gelation occur. Before the gel is formed, cyclic species undergo an acid-catalyzed ring-opening copolymerization with silica to produce a random copolymer. Other intermediates of the Q ij type (where Q indicates a four-functional silicon, the first subscript indicates the number of siloxane bridges connected to the silicon site, and the second subscript indicates the number of silanol groups) that develop before the gel is formed have also been identified. Spectral peak patterns of the final hybrid, observed in solid-state 29 Si and 13 C-NMR spectra, are also discussed.

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In this work, it has been investigated whether photonic density of states maps can be applied to the design of photonic crystal-based devices. For this reason, comparison between photonic density of states maps and transmittance maps was carried out. Results of comparison show full correspondence between these characteristics. Photonic density of states maps appear to be preferable for the design of photonic crystal devices, than photonic band gap maps presented earlier and than transmittance maps shown in the paper.Comment: 5 pages, 6 figure

The authors experimentally demonstrate self-diffraction effect in a hybrid material. Patterns at different light intensity levels were obtained. A dependence of the number of diffraction rings with the intensity of laser is observed.