Secondary factors contributing to the formation of amphiphilic type thermotropic liquid krystals of quaternary ammonyun salts

ΕΙΝΑΙ ΓΝΩΣΤΟ ΟΤΙ ΑΜΦΙΦΙΛΙΚΑ ΜΟΡΙΑ ΕΜΦΑΝΙΖΟΥΝ ΥΓΡΟ ΚΡΥΣΤΑΛΛΙΚΟ ΧΑΡΑΚΤΗΡΑ.ΣΤΗΝ ΠΑΡΟΥΣΑ ΕΡΓΑΣΙΑ ΕΓΙΝΕ ΠΕΡΑΙΤΕΡΩ ΜΕΛΕΤΗ ΤΩΝ ΠΑΡΑΓΟΝΤΩΝ ΠΟΥ ΕΠΗΡΕΑΖΟΥΝ ΤΗΝ ΟΡΓΑΝΩΣΗ ΑΜΦΙΦΙΛΙΚΩΝ ΜΟΡΙΩΝ ΚΑΙ ΤΟ ΣΧΗΜΑΤΙΣΜΟ ΘΕΡΜΟΤΡΟΠΙΚΩΝ ΥΓΡΩΝ ΚΡΥΣΤΑΛΛΙΚΩΝ ΦΑΣΕΩΝ.ΣΥΓΚΕΚΡΙΜΕΝΑ, ΧΡΗΣΙΜΟΠΟΙΗΘΗΚΑΝ ΤΕΤΑΡΤΟΓΕΝΗ ΑΜΜΩΝΙΑΚΑ ΑΛΑΤΑ ΜΕ ΜΕΓΑΛΗ ΑΛΕΙΦΑΤΙΚΗ ΑΛΥΣΙΔΑ,ΤΑ ΟΠΟΙΑ ΤΡΟΠΟΠΟΙΗΘΗΚΑΝ ΜΕ ΤΗΝ ΕΙΣΑΓΩΓΗ ΠΛΕΥΡΙΚΗΣ ΑΛΕΙΦΑΤΙΚΗΣ ΑΛΥΣΙΔΑΣ ΠΟΥ ΦΕΡΕΙ ΕΝΑ ΤΗΣ ΑΚΡΟ ΧΑΡΑΚΤΗΡΙΣΤΙΚΗ ΟΜΑΔΑ ΜΕ ΔΥΝΑΤΙΟΤΗΤΑ ΕΙΤΕ ΜΕΣΩ ΔΥΝΑΜΕΩΝ ΔΙΠΟΛΟΥ-ΔΙΠΟΛΟΥ (CN) Ή ΜΕ ΤΟ ΣΧΗΜΑΤΙΣΜΟ ΔΕΣΜΩΝ ΥΔΡΟΓΟΝΟΥ (OH,COOH) ΝΑ ΕΠΗΡΕΑΣΕΙ ΤΗ ΔΟΜΗ ΤΩΝ ΚΡΥΣΤΑΛΛΙΚΩΝ ΚΑΙ ΤΩΝ ΥΓΡΩΝ ΚΡΥΣΤΑΛΛΙΚΩΝ ΦΑΣΕΩΝ.Η ΚΑΘΑΡΟΤΗΤΑ ΚΑΙ Η ΠΙΣΤΟΠΟΙΗΣΗ ΤΗΣ ΜΟΡΙΑΚΗΣ ΔΟΜΗΣ ΤΩΝ ΕΝΩΣΕΩΝ ΕΓΙΝΕ ΜΕ ΣΤΟΙΧΕΙΑΚΗ ΑΝΑΛΥΣΗ ΚΑΙ ΦΑΣΜΑΤΟΣΚΟΠΙΑ ΠΥΡΗΝΙΚΟΥ ΜΑΓΝΗΤΙΚΟΥ ΣΥΝΤΟΝΙΣΜΟΥ.Η ΥΠΑΡΞΗ ΔΙΑΜΟΡΙΑΚΩΝ ΔΕΣΜΩΝ ΥΔΡΟΓΟΝΟΥ ΔΙΑΠΙΣΤΩΘΗΚΕ ΜΕ ΦΑΣΜΑΤΟΣΚΟΠΙΑ ΥΠΕΡΥΘΡΟΥ.Η ΘΕΡΜΙΚΗ ΣΤΑΘΕΡΟΤΗΤΑ ΤΩΝ ΠΡΟΙΟΝΤΩΝ ΕΛΕΓΧΘΗΚΕ ΜΕ ΘΕΡΜΟΣΤΑΘΜΙΚΗ ΑΝΑΛΥΣΗ.Ο ΣΧΗΜΑΤΙΣΜΟΣ ΥΓΡΩΝ ΚΡΥΣΤΑΛΛΙΚΩΝ ΦΑΣΕΩΝ ΔΙΑΠΙΣΤΩΘΗΚΕ ΜΕ ΟΠΤΙΚΗ ΜΙΚΡΟΣΚΟΠΙΑ ΚΑΙ ΔΙΑΦΟΡΙΚΗ ΘΕΡΜΙΔΟΜΕΤΡΙΚΗ ΣΑΡΩΣΗ ΚΑΙ Η ΜΕΤΡΗΣΗ ΤΩΝ ΓΕΩΜΕΤΡΙΚΩΝ ΠΑΡΑΜΕΤΡΩΝ ΤΩΝ ΚΡΥΣΤΑΛΛΙΚΩΝ ΚΑΙ ΤΩΝ ΥΓΡΩΝ ΚΡΥΣΤΑΛΛΙΚΩΝ ΦΑΣΕΩΝ ΠΡΑΓΜΑΤΟΠΟΙΗΘΗΚΕ ΜΕ ΠΕΡΙΘΛΑΣΗ ΑΚΤΙΝΩΝ Χ ΚΑΙ ΘΕΡΜΟΔΙΑΣΤΟΛΟΜΕΤΡΙΑ.ΑΠΟ ΤΑ ΑΠΟΤΕΛΕΣΜΑΤΑ ΠΟΥ ΕΛΗΦΘΗΣΑΝ ΠΙΣΤΟΠΟΙΗΘΗΚΕ ΟΤΙ ΟΛΑ ΤΑ ΠΡΟΙΟΝΤΑ ΣΧΗΜΑΤΙΖΟΥΝ ΥΓΡΕΣ ΚΡΥΣΤΑΛΛΙΚΕΣ ΦΑΣΕΙΣ (ΣΜΗΓΜΑΤΙΚΕΣ Α ΚΑΙ Τ) ΜΕ ΕΞΑΙΡΕΣΗ ΤΑ ΥΔΡΟΞΥ ΠΑΡΑΓΩΓΑ ΜΕ ΠΛΕΥΡΙΚΗ ΑΛΥΣΙΔΑ ΔΥΟ ΑΤΟΜΩΝ ΑΝΘΡΑΚΑ.(ΑΠΟΚΟΠΗ ΠΕΡΙΛΗΨΗΣ)ON THE BASIS OF THE RELATIONSHIP BETWEEN AMPHIPHILIC CHARACTER AND LIQUID CRYSTALLINITY WE INVESTIGATED SECONDARY FACTORS AFFECTING THE LIQUID CRYSTALLINE CHARACTER OF AMPHIPHILIC MOLECULES.SPECIFICALLY AMPHIPHILIC QUATERNARY AMMONIUM SALTS HAVE BEEN USED BEARING LONG (MAIN) ALIPHATIC CHAINS MODIFIED BY THE INTRODUCTION OF A SPACER GROUP WHICH BEARS AT ITS END A CHARACTERISTIC GROUP.THIS GROUP MAY LEAD TO DIMERIZATION OF THE MOLECULES EITHER DUE TO DIPOLE-DIPOLE (CN) OR THROUGH THE FORMATION OF HYDROGEN BONDING (OH,COOH).THE PURITY AND THE MOLECULAR STRUCTURE OF THE QUATERNARY AMMONIUM SALTS HAD BEEN TESTED WITH ELEMENTARY ANALYSIS AND NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY.THE EXISTENCE OF INTERMOLECULAR HYDROGEN BONDING FORMATION WAS ESTABLISHED BY FT-IR SPECTROSCOPY AND THE STABILITY OF THE MATERIALS WAS EVALUATED WITH THERMOGRAVIMETRY.THE FORMATION OF LIQUID CRYSTALLINE PHASES WAS SHOWN BY OPTICAL POLARIZED MICROSCOPY AND DIFFERENTIAL SCANNING CALORIMETRY AND ESTABLISHED BY X-RAY DIFRACTION AND DILATOMETRY.WITH THE LATER METHODS THE GEOMETRICAL PARAMETERS OF THE CRYSTALLINE AND LIQUID CRYSTALLINE PHASES WERE DETERMINED.IT WAS ESTABLISHED THAT ALL QUATERNARY AMMONIUM SALTS FORM LIQUID CRYSTALLINE PHASES (SMETIC A AND T PHASES) WITH THE EXCEPTION OF THE HYDROXY DERIVATIVES WITH A SIDE CHAIN OF THE TWO CARBON ATOMS.(ΑΠΟΚΟΠΗ ΠΕΡΙΛΗΨΗΣ

Actinide Ion (Americium-241 and Uranium-232) Interaction with Hybrid Silica–Hyperbranched Poly(ethylene imine) Nanoparticles and Xerogels

The binding of actinide ions (Am(III) and U(VI)) in aqueous solutions by hybrid silica–hyperbranched poly(ethylene imine) nanoparticles (NPs) and xerogels (XGs) has been studied by means of batch experiments at different pH values (4, 7, and 9) under ambient atmospheric conditions. Both materials present relatively high removal efficiency at pH 4 and pH 7 (>70%) for Am(III) and U(VI). The lower removal efficiency for the nanoparticles is basically associated with the compact structure of the nanoparticles and the lower permeability and access to active amine groups compared to xerogels, and the negative charge of the radionuclide species is formed under alkaline conditions (e.g., UO2(CO3)34− and Am(CO3)2−). Generally, the adsorption process is relatively slow due to the very low radionuclide concentrations used in the study and is basically governed by the actinide diffusion from the aqueous phase to the solid surface. On the other hand, adsorption is favored with increasing temperature, assuming that the reaction is endothermic and entropy-driven, which is associated with increasing randomness at the solid–liquid interphase upon actinide adsorption. To the best of our knowledge, this is the first study on hybrid silica–hyperbranched poly(ethylene imine) nanoparticle and xerogel materials used as adsorbents for americium and uranium at ultra-trace levels. Compared to other adsorbent materials used for binding americium and uranium ions, both materials show far higher binding efficiency. Xerogels could remove both actinides even from seawater by almost 90%, whereas nanoparticles could remove uranium by 80% and americium by 70%. The above, along with their simple derivatization to increase the selectivity towards a specific radionuclide and their easy processing to be included in separation technologies, could make these materials attractive candidates for the treatment of radionuclide/actinide-contaminated water

Dendritic Polymers in Tissue Engineering: Contributions of PAMAM, PPI PEG and PEI to Injury Restoration and Bioactive Scaffold Evolution

The capability of radially polymerized bio-dendrimers and hyperbranched polymers for medical applications is well established. Perhaps the most important implementations are those that involve interactions with the regenerative mechanisms of cells. In general, they are non-toxic or exhibit very low toxicity. Thus, they allow unhindered and, in many cases, faster cell proliferation, a property that renders them ideal materials for tissue engineering scaffolds. Their resemblance to proteins permits the synthesis of derivatives that mimic collagen and elastin or are capable of biomimetic hydroxy apatite production. Due to their distinctive architecture (core, internal branches, terminal groups), dendritic polymers may play many roles. The internal cavities may host cell differentiation genes and antimicrobial protection drugs. Suitable terminal groups may modify the surface chemistry of cells and modulate the external membrane charge promoting cell adhesion and tissue assembly. They may also induce polymer cross-linking for healing implementation in the eyes, skin, and internal organ wounds. The review highlights all the different categories of hard and soft tissues that may be remediated with their contribution. The reader will also be exposed to the incorporation of methods for establishment of biomaterials, functionalization strategies, and the synthetic paths for organizing assemblies from biocompatible building blocks and natural metabolites

Lamellar Tetragonal Symmetry of Amphiphilic Thermotropic Ionic Liquid Crystals in the Framework of Other Closely Related Highly Ordered Structures

An overview of the chemical compounds forming the rare smectic T phases is presented with references to the historical context. Thermodynamics (transition temperatures, enthalpies) along with the factors (stereochemical constraints, electrostatic interactions, aliphatic chain stacking, intermolecular forces) contributing to the adoption of tetragonal scaffolds are also discussed. Characteristic optical microscopy textures and X-ray diffraction patterns are presented. In parallel, a comparison of the geometrical parameters such as distances between atoms, molecular areas, volumes, and lattice parameters with the closest two-dimensional and three-dimensional organizations, is performed

Lamellar Tetragonal Symmetry of Amphiphilic Thermotropic Ionic Liquid Crystals in the Framework of Other Closely Related Highly Ordered Structures

An overview of the chemical compounds forming the rare smectic T phases is presented with references to the historical context. Thermodynamics (transition temperatures, enthalpies) along with the factors (stereochemical constraints, electrostatic interactions, aliphatic chain stacking, intermolecular forces) contributing to the adoption of tetragonal scaffolds are also discussed. Characteristic optical microscopy textures and X-ray diffraction patterns are presented. In parallel, a comparison of the geometrical parameters such as distances between atoms, molecular areas, volumes, and lattice parameters with the closest two-dimensional and three-dimensional organizations, is performed

Dendritic Polymers in Tissue Engineering: Contributions of PAMAM, PPI PEG and PEI to Injury Restoration and Bioactive Scaffold Evolution

The capability of radially polymerized bio-dendrimers and hyperbranched polymers for medical applications is well established. Perhaps the most important implementations are those that involve interactions with the regenerative mechanisms of cells. In general, they are non-toxic or exhibit very low toxicity. Thus, they allow unhindered and, in many cases, faster cell proliferation, a property that renders them ideal materials for tissue engineering scaffolds. Their resemblance to proteins permits the synthesis of derivatives that mimic collagen and elastin or are capable of biomimetic hydroxy apatite production. Due to their distinctive architecture (core, internal branches, terminal groups), dendritic polymers may play many roles. The internal cavities may host cell differentiation genes and antimicrobial protection drugs. Suitable terminal groups may modify the surface chemistry of cells and modulate the external membrane charge promoting cell adhesion and tissue assembly. They may also induce polymer cross-linking for healing implementation in the eyes, skin, and internal organ wounds. The review highlights all the different categories of hard and soft tissues that may be remediated with their contribution. The reader will also be exposed to the incorporation of methods for establishment of biomaterials, functionalization strategies, and the synthetic paths for organizing assemblies from biocompatible building blocks and natural metabolites

Dendritic Polymers as Promising Additives for the Manufacturing of Hybrid Organoceramic Nanocomposites with Ameliorated Properties Suitable for an Extensive Diversity of Applications

As the field of nanoscience is rapidly evolving, interest in novel, upgraded nanomaterials with combinatory features is also inevitably increasing. Hybrid composites, offer simple, budget-conscious and environmental-friendly solutions that can cater multiple needs at the same time and be applicable in many nanotechnology-related and interdisciplinary studies. The physicochemical idiocrasies of dendritic polymers have inspired their implementation as sorbents, active ingredient carriers and templates for complex composites. Ceramics are distinguished for their mechanical superiority and absorption potential that render them ideal substrates for separation and catalysis technologies. The integration of dendritic compounds to these inorganic hosts can be achieved through chemical attachment of the organic moiety onto functionalized surfaces, impregnation and absorption inside the pores, conventional sol-gel reactions or via biomimetic mediation of dendritic matrices, inducing the formation of usually spherical hybrid nanoparticles. Alternatively, dendritic polymers can propagate from ceramic scaffolds. All these variants are covered in detail. Optimization techniques as well as established and prospected applications are also presented

Thermal Spray Multilayer Ceramic Structures with Potential for Solid Oxide Cell Applications

The objective of this paper is to manufacture free-standing solid oxide cells (SOCs) through the atmospheric plasma spray process (APS), without the aid of a metallic support nor the need for a post-process heating treatment. A five-layered cell was fabricated. Fused and crushed yttria-stabilized zirconia (YSZ) powder in the 5–22 μm particle size range was used in order to achieve a dense electrolyte layer, yet still permitting satisfactory ionic diffusivity. Nickel oxide (NiO) powder that was obtained by in-house flame spray (FS) oxidation of pure nickel (Ni) powder was mixed and sprayed with the original Ni-YSZ feedstock, so as to increase the porosity content in the supporting electrode. Two transition layers were sprayed, the first between the support electrode and the electrolyte (25% (Ni/NiO)–75% YSZ) and the second at the electrolyte and the end electrode interface (50% YSZ–50% lanthanum strontium manganite (LSM)). The purpose of intercalation of these transition layers was to facilitate the ionic motion and also to eliminate thermal expansion mismatches. All the as-sprayed layers were separately tested by an in-house developed acetone permeability comparative test (APCT). Electrodes with adequate porosity (25–30%) were obtained. Concerning electrolytes, relatively thick (150–200 µm) layers derived from fused and crushed YSZ were found to be impermeable to acetone, while thinner YSZ counterparts of less than 100 µm showed a low degree of permeability, which was attributed mostly to existent microcracks and insufficient interparticle cohesion, rather than to interconnected porosity