Hydration of triethylenetetramine based inhibitor film accelerates the chloride-induced corrosion in concrete: a molecular dynamics study

Abstract. Organic corrosion inhibitors can be used to prevent chloride-induced corrosion in reinforced concrete structures. In this theoretical study Molecular Mechanics (MM) and Molecular Dynamics (MD) simulations are performed in order to better understand the interaction mechanisms with the passive film present on steel [1], in particular considering γ-FeOOH surface as solid surface which can be subject to chloride-induced corrosion process and the dimethylethanolamine (TETA) film [2]. The MD simulations are a very useful tool because they describe at atomistic level both the solid surface and organic inhibitors molecules in presence of chloride ions [2] and water molecules [3]. Hydration of organic TETA inhibitor film in presence of chloride ions always accelerate the corrosion process, as experimentally well known. In this theoretical work water molecules in fact induce chloride ions to adsorb on γ-FeOOH surface more quickly and in greater numbers respect with to the same simulations study without water molecules. This kind of organic film cannot exhibit a good behavior to prevent the chloride-induced corrosion process not displaying the so important repulsion to chloride ions. The hydration accelerates the corrosion process. This theoretical work permit to compare these results with another organic inhibitors films studied in previous work [1] in order to prevent the corrosion. References [1] M.V. Diamanti, E. A. Pérez-Rosales, G. Raffaini, F. Ganazzoli, A. Brenna, M. Pedeferri, M. Ormellese, Corrosion Science, 100, 231-241 (2015). [2] G. Raffaini, M. Catauro, F. Ganazzoli, F. Bolzoni, M. Ormellese, Macromolecular Symposia, 395, Article Number: 2000231, pp. 1-3 (2021). [3] G. Raffaini, F. Ganazzoli, J. of Biomed. Mat. Res. PART A, 92A, 1382-1391 (2006)

Molecular Dynamics Study of Sorafenib Anti-Cancer Drug: Inclusion Complex in Amphiphilic Cyclodextrin

Cyclodextrins (CDs) are cyclic oligosaccharides able to solubilize hydrophobic drugs in water enhancing their bioavailability. Sorafenib (SOR) is a lipophilic oral multikinase inhibitor that impedes proliferation, angiogenesis, and invasion of cancer cells with low water-solubility. Recently, amphiphilic cyclodextrins (aCDs) have been investigated as possible nanocarrier for systemic administration of SOR increasing its bio-availability. A theoretical study about inclusion complexes of SOR drug and a model of aCD system using molecular mechanics (MM) and molecular dynamics (MD) methods is here reported. At first, the single molecule aCD (SC6OH, heptakis(2-O-oligo(ethylene oxide)-6-hexylthio)-β-CD bearing 14 units of ethylene-oxide at the CD secondary rim) and SOR drug are studied. Then, the interaction between aCD and SOR is investigated. The theoretical results display different types of interaction geometries. The most stable geometry of the host-guest complex showed the lowest potential and favorable interaction energy and the fluorine atoms of SOR drug molecule are directed toward the hydrophobic primary rim of the aCD, while the part of the SOR rich in oxygen atoms is directed toward the hydrophilic secondary rim. This theoretical result is in a good agreement with NMR data in literature about same aCD as host of Sorafenib anti-cancer drug

Self-­‐ordering in solution of a novel polyamidoaminoacid with a chiral arginine side chain

Polyamidoaminoacids (PAAC) are a new class of bioinspired polymers obtained by polyaddition of selected aminoacids with N,N'-methylenebisacrylamide. Here we report some results obtained for the first such polymer, ARGO7, obtained with arginine stereoisomers. The CD spectra of the ARGO7 isomers showed an important and unexpected indication of a self-ordered pH-dependent secondary structure that was however nearly unaffected by temperature, ionic strength and denaturating agents. Theoretical modeling studies of L-ARGO7 carried out with classical Molecular Dynamical simulations showed that it assumed a folded structure with a transoid arrangement of the main chain reminiscent of the protein hairpin motif due to the intramolecular interactions. Torsion angles along the backbone showed a similar distribution at pH 6 and 14 consistent with the similarity of the CD spectra from pH 6 onwards

Chemical functionalization of graphene surface as filler for rubber compounds

Over the last few years, the surface modification of fillers for high-level technological applications such as polymer composites for tyre industry, conductive inks and coatings has seen a considerable increase in interest since it can increase mechanical, electrical, and thermal properties of the final material. Nano-sized carbon allotropes such as graphene and carbon nanotubes are a suitable class of compounds for these purposes: high thermal and electrical conductivity along with considerable mechanical reinforcement are the main improvements that these fillers bring to the composite and their elevated surface area allows to reduce the filler volume ratio compared to more common alternatives. An efficient and reliable method to modify the surface of these nano-fillers is the so-called pyrrole methodology, a mild procedure that involves bio-sourced reagents to introduce functional groups on the graphitic planes and that has been recently employed in the fabrication of elastomeric composites with improved mechanical properties. In order to understand the mechanism beneath the interaction between the pyrrole and the substrate and thus the behavior of the functionalized filler, a more in-depth analysis is requested. A theoretical work based on molecular dynamics simulations and a DFT study were performed in order to investigate the interaction energy, the geometry of interaction and the mobility of N-substituted pyrrole molecules adsorbed on the graphene planes. This theoretical study at atomistic level can help design a new class of high-performance fillers by better understanding the interaction mechanism given the important role of supramolecular interactions

A Molecular Dynamics Study of Noncovalent Interactions between Rubber and Fullerenes

The percolation and networking of filler particles is an important issue in the field of rubber reinforcement, and much effort is given to clarify the true nature of the reinforcement mechanism and the viscoelastic behavior. The concentration of nanofillers also in the presence of large amounts of carbon black is a parameter that can influence the macroscopic rubber behavior. In this paper, noncovalent interactions between C60 fullerenes with poly-1,4-cis-isoprene (PI) either as such or modified are studied through atomistic simulations based on molecular mechanics (MM) and molecular dynamics (MD) methods. At first, the conformational properties of a single chain and of 12 PI chains in a periodic simulation box are studied. Afterwards, the conformational properties of a single PI chain polymer terminated with a -COOH group, and then a bulk system formed by chains of unmodified and some PI modified chains are considered. Then, the systems formed by adding fullerenes to these two different bulk systems are studied. Relatively small interaction energy between rubber and fullerenes being well dispersed in the sample is found. The simulations showed a preferential tendency of fullerenes to display self-aggregation, in the presence of even a small fraction of modified polymer chains

Organic Inhibitors to Prevent Chloride-Induced Corrosion in Concrete: Atomistic Simulations of Triethylenetetramine-Based Inhibitor Film

Inhibitors are largely used to prevent chloride-induced corrosion in reinforced concrete structures thanks to both a barrier effect on chloride penetration and a competition with the adsorption of the inhibitor. The interaction mechanisms between passive film on carbon steel, the inhibitor molecule, and chlorides still require deeper understanding. Theoretical studies based on molecular mechanics (MM) and molecular dynamics (MD) methods can be useful to better understand the passive film formation and its interaction with chlorides. In this work, the interaction between a triethylenetetramine (TETA) inhibitor film on γ-FeOOH surface and chlorides is studied using MD methods. After MM optimization in the initial adsorption stage, some chlorides are close to protective TETA film. After MD run at room temperature effectively, chlorides remain close to the protective film. In order to have an effective barrier on chloride attack, the metal oxide must remain wholly covered by the protective film. The TETA film well covers the lepidocrocite surface but cannot kinetically efficiently prevent the chloride-induced corrosion compared to other organic films exposing COO− groups because it does not exert any repulsion to chlorides

Sol-gel synthesis, thermal characterization, surface interactions and release of Silica/drug hybrids system

Local drug release in the implant material for medical applications appears to be a very interesting alternative to systemic therapy. The possibility of introducing drug release systems into the implant site has been widely studied and used. The aim of this work is synthesized by sol- gel process a system composed by SiO2 glass and ketoprofen, anti-inflammatory drug. Two percentage of drug (5 and 15wt%) were entrapped in Silica matrix via sol-gel method and dried materials were analysed through Fourier transformed infrared spectroscopy (FTIR), simultaneous DSC/TGA analysis. The drug loaded amorphous bioactive materials were studied in terms of their drug release kinetics. A theoretical study based on Molecular Mechanics and Molecular Dynamics methods is a work in progress to investigate possible surface interactions between the silica-based surface and the ketoprofen drug molecules both at small and higher concentration for useful comparison with experimental data

Algunos criterios para el análisis y evaluación del uso de las TICS en educación. Una experiencia en la práctica docente inicial

Esta ponencia se enmarca en un Proyecto de Mejoramiento de la Enseñanza de Grado, (PIIMEG-2011-2013), llevado a cabo en la Universidad Nacional de Río Cuarto, denominado: Incorporación de las TICs a la Enseñanza: Acciones situadas y fundadas del estudiante en su Formación Docente.El objetivo general del mismo es: Promover el uso de las TICs, como herramienta de enseñanza a partir de la potencialidad educativa y de las formas de inclusión en situaciones educativas actuales del nivel secundario.El propósito de esta ponencia es presentar una experiencia realizada en la práctica docente inicial de los alumnos del Profesorado en Ciencias Biológica de la UNRC. Consiste en la incorporación de las TICs en las programaciones didácticas y la implementación de un proceso de enseñanza en una escuela secundaria donde realiza de manera colaborativa e interagencial la práctica docente inicial.El análisis y valoración del uso de las TICs posibilitó y exigió elaborar criterios que se presentarán en esta ponencia entre ellos: TICs usadas, pertinencia del uso, la finalidad del uso, el momento del proceso de enseñanza y de aprendizaje en el que se emplean y modalidad de implementación.Considerando los planteos realizados en las políticas educativas en relación con la alfabetización digital y la promoción del uso de computadora, se podría afirmar que la implementación de las TICs en la enseñanza y su evaluación es una problemática sentida y considerada de importancia, de allí su presentación en este evento. Se espera no solo la socialización de los criterios construidos y evaluaciones realizadas sino también ampliar las perspectivas de análisis y evaluación con los aportes de los asistentes

Self-Structuring in Water of Polyamidoamino Acids with Hydrophobic Side Chains Deriving from Natural α-Amino Acids

This paper reports on synthesis, acid-base properties and self-structuring in water of chiral polyamidoamino acids (PAACs) obtained by polyaddition of N,N'-methylenebisacrylamide with L-alanine, L-valine and L-leucine (M-L-Ala, M-L-Val, M-L-Leu) with potential for selective interactions with biomolecules. The polymers maintained the acid-base properties of amino acids. In water, the circular dichroism spectra of PAACs revealed pH-dependent structuring in the range 3-11 and in the wavelength interval 200-280 nm. Taking as reference the values at pH 3, the differential molar ellipticities were plotted in the pH interval 3-11. Sigmoidal curves were obtained presenting inflection points at pH 8.1, 6.8 and 7.3 for M-L-Ala, M-L-Val and M-L-Leu, respectively, corresponding to the amine half-ionization. Theoretical modeling showed that PAACs assumed stable folded conformations. Intramolecular interactions led to transoid arrangements of the main chain reminiscent of protein hairpin motif. Oligomers with ten repeat units had simulated gyration radii consistent with the hydrodynamic radii obtained by dynamic light scattering