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Three vertically etched (grooved) silicon structures with lattice constants of 16, 8 and 4 µm were prepared and tested as 1D photonic crystals for applications in the infrared range of the electromagnetic spectrum. These structures with high contrast in the refractive index (n Si /n air = 3.42/1) not only possess a wide main band gap for the photons, but these have also reasonably wide side stop bands at lower wavelengths. The IR reflectance spectra for such structures simulated using the method of characteristic matrix showed a good agreement with the experimental data.

Morphology and molecular structure of three nascent ultra high molecular weight polyethylene (UHMWPE) powders synthesized on unsupported and supported Ziegler-Natta heterogeneous catalysts were studied with the help of electron microscopy and infrared (IR) spectroscopy. A synthesis was carried out in a slurry process in n-heptane at a temperature of about 70°C, which resulted in production of UHMWPE of one and the same molecular weight, approaching 10 6 g/mol. The morphology of the nascent particles dramatically differed, however, which is evidence of the important role of the catalytic system used. Nascent particles synthesized on unsupported TiCl 4 catalyst with EtAl as the cocatalyst had a globular structure, while those synthesized on supported TiCl 4 /Al 2 O 3 ؒSiO 2 and TiCl 3 ؒ0.3 AlCl 3 /MgCl 2 Ziegler-Natta catalysts with the same cocatalyst demonstrated fibrillar (cobweb) and spiral (wormlike) structures, respectively. As revealed by IR spectroscopy, there was a significant difference in the nature of the crystalline regions formed during the synthesis/crystallization process; in the amount of short trans sequences not included in crystallites (taut tie molecules); in the content of irregular conformers of various types, including typical point de-*Dedicated to Prof. Francisco J. Baltá Calleja on the occasion of his 65th 814 IVAN'KOVA ET AL.fects 2G1 kinks; and so on. The melt-crystallized films produced from the investigated reactor powders were markedly distinguished by their drawability and by the existence and the amount of different molecular conformations despite a sufficiently high recrystallization temperature and prolonged preheating. The difference in molecular structure of the drawn films was retained in a whole range of draw ratios. It is concluded that there is a well-pronounced "memory effect" and the morphology of the original nascent particles depending on the catalyst/synthesis conditions clearly play a role in the properties of the end product.

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