Maria Owińska

Amine-functionalized polysiloxanes, due to the presence of amino moieties, can be used for the extraction of toxic metal ions from wastewater, as supports for metallic catalysts, stabilizers for metal nanoparticles, macromolecular biocides, or as self-healing materials. In the present work, we studied poly(hydromethylsiloxane) (PHMS) networks functionalized with three amines: N-allyaniline (Naa), N-allylcyclohexylamine (Nach), and N-allylpiperidine (Nap). They were prepared using two procedures. The first one was a two-step process in which the previously cross-linked PHMS was reacted with the amine. The second, one-step method involved simultaneous PHMS cross-linking and reaction with the amine. FTIR and ²⁹Si MAS-NMR spectroscopic investigations, as well as elemental analysis, allowed us to conclude that the one-step method was more advantageous. It ensured higher PHMS networks functionalization degrees and hindered hydrolysis/condensation of Si-H/SiOH groups side processes, which were related to the basicity of the studied amines and significant in the two-step procedure.

Polymers containing biocidal moieties (e.g., amino or ammonium groups) are considered promising materials that can help combat the growing resistance of pathogens to commonly used antimicrobials. Searching for new polymeric biocides, in this work, non-porous and porous poly(hydromethylsiloxane) (PHMS) networks were prepared and post-functionalized by N-allylaniline (Naa). Non-porous networks were obtained by cross-linking PHMS in the bulk and porous—in W/O high-internal-phase emulsion (HIPE). Linear divinyldisiloxane (M₂^Vi) or cyclic tetravinyltetrasiloxane (D₄^Vi) were used as cross-linkers. Studies confirmed the expected non-porous and open macroporous microstructure of the initial networks. They also showed that functionalization by Naa was more efficient for the non-porous networks that swelled to lower extents in toluene and contained higher amounts of Si-H groups than the porous ones. In the reactions with benzyl chloride or 1-bromoctane, some amino groups present in these materials were transformed to ammonium groups. It was found that activity against Gram-positive S. aureus and Gram-negative E. coli bacteria depended on the functionalization degree, cross-linking level and the microstructure of the modified materials.

The kinetics of Ho(III) extraction using di(2‐ethylhexyl)phosphoric acid (D2EHPA) under the influence magnetic field are examined. The methodology for kinetics research is based on spectrophotometric techniques. Initial experiments without a magnetic field assess the influence of Ho(III) concentration (0.00625–0.1 m), pH (1–6), D2EHPA concentration (0.1–2 m), and temperatures (5–35 °C). Subsequent tests (5–35 °C) determine the influence of the magnetic field. Experimental considerations are supplemented with numerical simulations of the magnetic field affecting the extraction system. A white precipitate formed at the phase boundary is characterized using X‐ray fluorescence (XRF), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), and X‐ray photoelectron spectroscopy (XPS) techniques. Post‐extraction solutions are analyzed with nuclear magnetic resonance (NMR) spectroscopy to investigate the structure and magnetic properties of the D2EHPA‐Ho(III) complex. The conducted research indicate that magnetic fields notably enhance kinetics of extraction above 25 °C, suggesting a possible change in the extraction mechanism.

A silicon oxycarbide-carbon nanotube coating on steel was synthesized using a novel approach utilizing unmodified carbon nanotubes (CNT), silane surfactant and large monomer-based silsesquioxane sol. This enabled the creation of very stable carbon nanotube dispersion, which in turn resulted in homogenous layers obtained in a simple dip-coating process. The samples were annealed in 800 °C in argon to obtain a uniform glassy silicon oxycarbide-based composite from a silsesquioxane precursor. The layers’ morphology and nanomechanical properties were investigated using a number of methods, including infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation, Accelerated Property Mapping (XPM) and Quantitative Nanomechanical Mapping—an Atomic Force Microscopy method (QNM-AFM).

It has been shown that bifunctional monomers (D units), which are used to increase the carbon content in silicon oxycarbide precursors, can form volatile oligomers, thus affecting the amount of carbon available during the transition into the final material in the annealing process. Additionally, an uneven distribution of carbon-rich mers may lead to the formation of a free-carbon phase, instead of the incorporation of carbon atoms into the silicon matrix. In this study, a novel two-step approach was utilized. Firstly, a macromonomer containing a number of structural units with precise structure was synthesized, which was later polycondensed into a ceramic precursor. Chlorodimethylsilane modified 2,4,6,8-tetramethylcyclotetrasiloxane was used as a silicon oxycarbide precursor monomer containing both T and D structural units (i.e., silicon atoms bonded to three and two oxygen atoms, respectively), with well-defined interconnections between structural units. Such a macromonomer prevents the formation of small siloxane rings, and has a very limited number of possible combinations of structural units neighboring each silicon atom. This, after investigation using IR, XRD, TG and elemental analysis, gave insight into the effect of “anchoring” silicon atoms bonded to two methyl groups, as well as the impact of their distribution in comparison to the materials obtained using simple monomers containing a single silicon atom (structural unit).

Linear polyhydromethylsiloxane (PHMS) was functionalized with nitrogen-containing organic compounds:N-allylaniline (Naa),N-allylcyclohexylamine (Nach),N-allylpiperidine (Nap) and 4-vinylpyridine (4VP) via hydrosilylation reaction in the presence of Pt⁰complex (Karstedt’s catalyst) under mild conditions. Reaction course was followed by FTIR spectroscopy and final hydrosilylation products were characterized by FTIR,¹H,²⁹Si NMR and²⁹Si MAS-NMR spectroscopies as well as by elemental analysis. Results showed that functionalization of PHMS withN-allyl amines took place but in none of the systems it was complete. Hydrosilylation of Naa, Nach and Nap with PHMS led both, to the β and α addition products.²⁹Si NMR spectroscopy showed unequivocally that the reaction of PHMS with 4VP did not occur and the only reactions in the systems were hydrolysis of Si–H groups of PHMS followed by condensation of the silanol groups resulting in cross-linking of the polymer. All the functionalized polymers studied in the work contained reactive amine moieties prone to further modifications, therefore exhibit a great potential for various applications.