Macroporous Poly(hydromethylsiloxane) Networks as Precursors to Hybrid Ceramics (Ceramers) for Deposition of Palladium Catalysts.

Poly(hydromethylsiloxane) (PHMS) was cross-linked with 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (D4Vi) in water-in-oil High Internal Phase Emulsions to form macroporous materials known as polyHIPEs. It was shown that in the process of pyrolysis under Ar atmosphere at 520 °C, the obtained polyHIPEs were converted to ceramers with high yields (82.8-88.0 wt.%). Structurally, the obtained ceramers were hybrid ceramics, i.e., they consisted of Si-O framework and preserved organic moieties. Macropores present in the polyHIPE precursors remained in ceramers. Ceramers contained also micro- and mesopores which resulted from the precursor's mass loss during pyrolysis. Total pore volume and BET specific surface area related to the existence of micro- and mesopores in ceramers depended on the PHMS: D4Vi ratio applied in polyHIPE synthesis. The highest total pore volume (0.143 cm3/g) and specific surface area (344 m2/g) were reached after pyrolysis of the precursor prepared with the lowest amount of D4Vi as compared to PHMS. The composite materials obtained after deposition of PdO nanoparticles onto ceramers followed by reduction of PdO by H2 were active and selective catalysts for phenylacetylene hydrogenation to styrene.

Quantitative and qualitative analyses of drug adsorption on silver nanoparticle monolayers: QCM, SERS, and TEIRA nanospectroscopy studies.

In this study for the first time, surface-enhanced Raman spectroscopy (SERS) and tip-enhanced infrared (TEIRA) nanospectrocopy together with a quartz crystal microbalance (QCM) are postulated as powerful tools for comprehensive qualitative and quantitative analyses of drug/metal nanocarrier conjugates. The development of efficient drug/carrier systems requires that the stability of the drug/carrier connection be estimated and the number of drug molecules immobilized on the carrier surface be determined. Thus, such a characterization study is highly desirable. Here, the SERS technique was applied to identify how erlotinib, a drug applied in non-small cell lung cancer (NSCLC) therapy, interacts with silver nanoparticles (AgNPs) that are considered as drug carriers. These investigations indicate that in the erlotinib/AgNP suspension, the drug strongly connects with the NPs mainly through the phenylacetylene moiety. The QCM was used to prepare an AgNP monolayer with a monitored degree of coverage and to perform controlled erlotinib adsorption as a next step. The results indicate that the drug forms a stable layer on the AgNP monolayer and also show the amount of the erlotinib molecules which underwent immobilization on the metal nanosurface. Simultaneously, it was identified how the erlotinib layer adsorbs on the AgNP monolayer using TEIRA nanospectroscopy with ultra-high spatial resolution. The obtained results show that the phenylacetylene, ethoxy, and methoxy moieties are mainly responsible for the drug/AgNP monolayer connection. Additionally, the performed studies also try to explain the surface-enhanced phenomena that occur during the TEIRA experiments and attempt to prove the statement that the "tip-enhanced" effect plays a crucial role in the detection of the thin erlotinib layer deposited on the AgNP monolayer.

Poly(methylvinylsiloxane)-Based High Internal Phase Emulsion-Templated Materials (polyHIPEs)-Preparation, Incorporation of Palladium, and Catalytic Properties.

Poly(methylvinylsiloxane) (V3 polymer) obtained by kinetically controlled anionic ring-opening polymerization of 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane was cross-linked with various amounts of 1,3,5,7-tetramethylcyclotetrasiloxane (D4 H) in w/o high internal phase emulsions (HIPEs). PolyHIPEs thus prepared differed in the polymer cross-linking degree, which affected their porous morphology and total porosity. The obtained V3 polymer-based polyHIPEs were applied as matrices for the incorporation of Pd from the Pd(OAc)2 solution in tetrahydrofuran. This process involved the conversion of Si-H groups remaining in the polymer networks and resulted in the formation of crystalline, metallic Pd in the systems. Mean sizes of the generated Pd crystallites were lower in polyHIPEs of higher than in those of lower polymer cross-linking degrees and porosities (∼5 nm vs ∼8 nm, respectively). The Pd-containing polyHIPEs showed activity in catalytic hydrogenation of the triple carbon-carbon bond in phenylacetylene giving the unsaturated product, styrene with a selectivity of ca. 80%. To the best of our knowledge, this is the first work devoted to polysiloxane-based polyHIPEs with dispersed metallic particles.