Rubber Toughened and Nanoparticle Reinforced Epoxy Composites

Epoxy resins have achieved acceptance as adhesives, coatings, and potting compounds, but their main application is as matrix to produce reinforced composites. However, their usefulness in this field still limited due to their brittle nature. Some studies have been done to increase the toughness of epoxy composites, of which the most successful one is the modification of the polymer matrix with a second toughening phase. Resin Transfer Molding (RTM) is one of the most important technologies to manufacture fiber reinforced composites. In the last decade it has experimented new impulse, due to its favorable application to produce large surface composites with good technical properties and at relative low cost. This research work focuses on the development of novel modified epoxy matrices, with enhanced mechanical and thermal properties, suitable to be processed by resin transfer molding technology, to manufacture Glass Fiber Reinforced Composites (GFRC’s) with improved performance in comparison to the commercially available ones. In the first stage of the project, a neat epoxy resin (EP) was modified using two different nano-sized ceramics: silicium dioxide (SiO2) and zirconium dioxide (ZrO2); and micro-sized particles of silicone rubber (SR) as second filler. Series of nanocomposites and hybrid modified epoxy resins were obtained by systematic variation of filler contents. The rheology and curing process of the modified epoxy resins were determined in order to define their aptness to be processed by RTM. The resulting matrices were extensively characterized qualitatively and quantitatively to precise the effect of each filler on the polymer properties. It was shown that the nanoparticles confer better mechanical properties to the epoxy resin, including modulus and toughness. It was possible to improve simultaneously the tensile modulus and toughness of the epoxy matrix in more than 30 % and 50 % respectively, only by using 8 vol.-% nano-SiO2 as filler. A similar performance was obtained by nanocomposites containing zirconia. The epoxy matrix modified with 8 vol.-% ZrO2 recorded tensile modulus and toughness improved up to 36% and 45% respectively regarding EP. On the other hand, the addition of silicone rubber to EP and nanocomposites results in a superior toughness but has a slightly negative effect on modulus and strength. The addition of 3 vol.-% SR to the neat epoxy and nanocomposites increases their toughness between 1.5 and 2.5 fold; but implies also a reduction in their tensile modulus and strength in range 5-10%. Therefore, when the right proportion of nanoceramic and rubber were added to the epoxy resin, hybrid epoxy matrices with fracture toughness 3 fold higher than EP but also with up to 20% improved modulus were obtained. Widespread investigations were carried out to define the structural mechanisms responsible for these improvements. It was stated, that each type of filler induces specific energy dissipating mechanisms during the mechanical loading and fracture processes, which are closely related to their nature, morphology and of course to their bonding with the epoxy matrix. When both nanoceramic and silicone rubber are involved in the epoxy formulation, a superposition of their corresponding energy release mechanisms is generated, which provides the matrix with an unusual properties balance. From the modified matrices glass fiber reinforced RTM-plates were produced. The structure of the obtained composites was microscopically analyzed to determine their impregnation quality. In all cases composites with no structural defects (i.e. voids, delaminations) and good superficial finish were reached. The composites were also properly characterized. As expected the final performance of the GFRCs is strongly determined by the matrix properties. Thus, the enhancement reached by epoxy matrices is translated into better GFRC´s macroscopical properties. Composites with up to 15% enhanced strength and toughness improved up to 50%, were obtained from the modified epoxy matrices

Nickel(II) Complexes with Three-Dimensional Geometry α‑Diimine Ligands: Synthesis and Catalytic Activity toward Copolymerization of Norbornene

A series of three-dimensional geometry 9,10-dihydro-9,10-ethanoanthracene-11,12-diimines (L1–L4) and their nickel­(II) dibromide complexes (C1–C4) were synthesized and characterized. The nickel complexes C1–C4, with three-dimensional geometry, exhibited very high activities for norbornene (NB) homopolymerization with only B­(C₆F₅)₃ as cocatalyst,: for C2 even up to 5.53 × 10⁷ g of polymer/((mol of Ni) h). To investigate the activation of polar monomer, complexes C2 and C3 were selected for copolymerization of NB and 5-norbornene-2-yl acetate (NB-OCOMe) in relatively high activities (1.6–5.8 × 10⁵g of polymer/((mol of Ni) h)) and high molecular weights ((0.2–2.8) × 10⁵ g/mol) as well as narrow molecular weight distributions (MWD < 2 for all polymers) depending on the variation of feed ratios. The reactivity ratios of the NB and NB-OCOMe monomers for C2/B­(C₆F₅)₃ system by the Kelen–Tüdös method were determined to be <i>r</i>_NB‑OCOMe = 0.05 and <i>r</i>_NB = 6.72, respectively. Moreover, the mechanism of polymerization catalyzed by the novel three-dimensional geometry nickel­(II) complexes was presented and supported by an end group analysis of the polymer and density functional theory (DFT) calculations of the reaction. The substituent effect of the catalysts and the interaction between Ni²⁺ and NB were discussed, and the results showed that α-diimine nickel complexes with greater steric hindrance and smaller HOMO–LUMO gaps could achieve higher reactivity

Number of different samples in the WCD dataset.

Number of different samples in the WCD dataset.</p

Structure of ISSD.

Structure of ISSD.</p

Validation results of components in the ISSD.

Validation results of components in the ISSD.</p

Growth of Semiconducting Single-Walled Carbon Nanotubes by Using Ceria as Catalyst Supports

The growth of semiconducting single-walled carbon nanotubes (s-SWNTs) on flat substrates is essential for the application of SWNTs in electronic and optoelectronic devices. We developed a flexible strategy to selectively grow s-SWNTs on silicon substrates using a ceria-supported iron or cobalt catalysts. Ceria, which stores active oxygen, plays a crucial role in the selective growth process by inhibiting the formation of metallic SWNTs via oxidation. The so-produced ultralong s-SWNT arrays are immediately ready for building field effect transistors

Identification of Potent and Selective RIPK2 Inhibitors for the Treatment of Inflammatory Diseases

NOD2 (nucleotide-binding oligomerization domain-containing protein 2) is an internal pattern recognition receptor that recognizes bacterial peptidoglycan and stimulates host immune responses. Dysfunction of NOD2 pathway has been associated with a number of autoinflammatory disorders. To date, direct inhibitors of NOD2 have not been described due to technical challenges of targeting the oligomeric protein complex. Receptor interacting protein kinase 2 (RIPK2) is an intracellular serine/threonine/tyrosine kinase, a key signaling partner, and an obligate kinase for NOD2. As such, RIPK2 represents an attractive target to probe the pathological roles of NOD2 pathway. To search for selective RIPK2 inhibitors, we employed virtual library screening (VLS) and structure based design that eventually led to a potent and selective RIPK2 inhibitor <b>8</b> with excellent oral bioavailability, which was used to evaluate the effects of inhibition of RIPK2 in various <i>in vitro</i> assays and <i>ex vivo</i> and <i>in vivo</i> pharmacodynamic models