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4 Materials Science Poland

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Nanogel formation by intrachain radiation-induced cross-linking. Simulation and experiment

100%

Ulański P. , Kadłubowski S. , Jeszka J. K.

Materials Science Poland

2006

tom Vol. 24, No. 2/2

467--476

Nanogel formation by intrachain radiation-induced cross-linking is described. The origin of dispersive kinetics observed in pulse radiolysis experiments and the influence of cross-linking method on nanogel structure are studied by the Monte-Carlo simulation. The simulations have been performed on an fcc lattice using the cooperative motion algorithm. The recombination kinetics is studied as a function of the chain length (20-1068 beads) and of the number of radicals generated per chain. It is shown that the radical recombination rate coefficients are time-dependent (dispersive kinetics) and the simulation results can be fitted using single "stretched exponential" (KWW) function for two radicals per chain and a sum of two KWW functions for a larger number of radicals. The nanogel structure (radius of gyration and loop lengths, related to the resistance of nanogels to scissions) has also been studied. It is found that in the case of instant radical generation, the increasing number of radicals leads to formation of smaller and smaller loops. Results of the simulations are compared with the pulse radiolysis experiment on poly(ethylene oxide) using a suitable scaling of MC time and unit length, and a good agreement is obtained.

Zone casting - a universal method of preparing oriented anisotropic layers of organic materials

100%

Tracz A. , Pakula T. , Jeszka J. K.

tom Vol. 22, No. 4

415--421

A method for the preparation of oriented, anisotropic layers of soluble molecular materials on substrates that were not pre-oriented (so-called zone casting) is presented. The method consists in casting a suitable solution, continuously supplied by a nozzle, onto a moving substrate. Solvent evaporation takes place from the surface of the meniscus formed between a special flat nozzle and the substrate. Due to a gradient of the solute concentration, its solidification proceeds in a narrow zone under highly anisotropic conditions. The conditions of stationary deposition and the influence of various parameters on the process, such as casting speed, the diffusion coefficient, evaporation rate, are discussed. It is shown that the zone casting can be used to obtain anisotropic layers of many different low-molecular-weight and macromolecular materials.

Conducting polymer films with new organic donor MDT-TSF: preparation and properties

75%

Tracz A. , Mierczyńska A. , Takimiya K. , Otsubo T. , Niihara N. , Jeszka J. K.

Materials Science Poland

2006

tom Vol. 24, No. 2/2

517--526

Preparation and properties of surface-conductive polymer composites based on a recently synthesized electron-donor, methylenedithio-tetraselenefulvalene (MDT-TSF) are described. Polycarbonate and biodegradable polyester polylactide are used as polymer matrices. The obtained surface-conductive materials with MDT-TSF polyiodides show high, metal-like conductivities, indicating that MDT-TSF is one of the best donors for conductive composites.

Synthesis of gold nanoparticles in solid state by thermal decomposition of an organometallic precursor

75%

Wostek-Wojciechowska D. , Jeszka J. K. , Uznanski P. U. , Amiens C. , Chaudret B. , Lecante P.

tom Vol. 22, No. 4

407--413

Gold nanoparticles were obtained directly in solid polymer films by thermal decomposition of the [O(Au(PPh3))3][BF4] precursor molecularly dispersed in the polymer and by decomposition of microcrystals on different supports. The nanoparticles were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis spectroscopy, and wide-angle X-ray scattering (WAXS). In spite of high precursor concentration, the size of the obtained nanoparticles was similar to those prepared in diluted solutions.