Piotr Pospiech

Gamma Globulins Adsorption on Carbofunctional Polysiloxane Microspheres

Polysiloxane microspheres containing a large number of silanol groups were functionalized by reactions of these groups with organic alkoxy or chlorosilanes having chloro, amine or imidazole functions in their organic parts. The obtained imidazole groups on the microspheres were ionized by the reaction with n-octyl iodide and with methyl iodide while the chloro functions were used for quaternization of a tertiary amine. Adsorption of gamma globulins on these functionalized microspheres was studied in aqueous suspension at pH 5.2, 7.4 and 9.2. Hydrophilic–hydrophobic properties of these microspheres were examined by measuring adsorption of a hydrophobic dye, Rose Bengal. The functionalized microspheres showed higher adsorption of globulins and higher hydrophobicity than the not functionalized ones rich in silanol groups. In the case of microspheres with ionic functional groups the electrostatic forces also contribute to attractive interactions between proteins and microspheres.

Soluble Alkylthiopolysiloxane-Supported Palladium Catalysts for the Heck Reaction

Soluble polysiloxanes with 2-butylthioethyl side groups have been used as support for palladium(II) catalyst. Catalytic activity of such immobilized palladium complex was tested in a model Heck reaction. The activity of the complex in terms of yield and turnover number was comparable to that of PdCl2(PhCN)2. Polysiloxane-supported catalyst shows good stability and low leaching, and its catalytic activity maintained practically unchanged through five catalytic cycles. According to XPS analysis, palladium in the complex with polysiloxane containing thioether groups appears as Pd(II).

Macroporous microspheres and microspheroidal particles from polyhydromethylsiloxane

AbstractPolysiloxane macroporous microspheres and macroporous spheroidal particles were generated from a linear siloxane polymer using a simple emulsion procedure. Osmotic pressure produced by nano-dispersed ionic salt solution in polysiloxane droplets formed in aqueous emulsion is proposed as a mechanism of macropore formation. The competition between cross-linking of the polymer and osmotic swelling of the microspheres governs the shape and porosity of the particles which were characterized by SEM, 29Si MAS NMR, mercury intrusion porosimetry, and X-ray computed tomography. Graphical Abstractᅟ

Bacterial cell killing properties of silver-loaded polysiloxane microspheres

Cross-linked polysiloxane microspheres containing a large number of SiOH groups were modified by introduction of organic thiol groups, which were further used for the functionalization of the microspheres with silver thiolate groups. The microspheres were characterized by 29Si MAS NMR, 13C MAS NMR, SEM, XPS and elemental analysis. They were tested as biocides against selected Gram-positive and Gram-negative bacteria strains and exhibited high bactericidal activity. Separately, linear polysiloxane polymers equipped with organothiol groups and loaded with silver were synthesized. Their antibacterial activity was compared with that of silver thiolate-functionalized microspheres. Different shape of particles and a different form of silver explained somewhat lower activity of polymers.

Terpolymers of N-vinylpyrrolidinone and 1-vinylimidazole as new supports for palladium nanocluster catalysts

Abstract Two terpolymers of styrene, divinylbenzene, and 1-vinylimidazole (S/DVB/VI) or N-vinylpyrrolidinone (S/DVB/NVP) were prepared by radical polymerization. Palladium nanoparticle catalyst has been “heterogenized” by anchoring to these polymers the [PdCl2(PhCN)2] complex via ligand exchange reaction. The formation of coordination bond between S/DVB/VI, S/DVB/NVP terpolymers and Pd2+ ions was studied using infrared and XPS. Immobilized palladium complex was reduced during hydrogenation reaction or by reaction with sodium borohydride. Characterization of polymer supports and palladium catalysts has involved the measurements of the structural parameters in the dry state by the nitrogen BET adsorption, X-ray photoelectron spectroscopy (XPS), AAS spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Both the catalytic systems were found efficient in the hydrogenation of cinnamaldehyde. The stability and a good recycling efficiency of these catalysts make them useful for prolonged use. The factors influencing selectivity of supported catalysts were discussed. The results offer the possibility of using these terpolymers for the immobilization of metal complex catalysts for hydrogenation and other catalytic reactions.