Search results for "Ionic polymerization"

Reversible coordination of dioxygen by tripodal tetraamine copper complexes incorporated in a porous silica framework.

2010

The present study reports the synthesis and rational design of porous structured materials by using a templating method. A tetraethoxysilylated tripodal tetraamine (TREN) was covalently incorporated in a silica framework with a double imprint: A surfactant template and a metal ion imprint. The presence of a cationic surfactant (CTAB) endowed the material with a high porosity, and the tripodal or square-pyramidal topology of the ligand was preserved thanks to the use of the silylated Cu(II) complex. After removal of the surfactant and de-metalation, the incorporated tetraamine was quantitatively complexed by CuCl(2) and the material has shown after thermal activation that a reversible bindin…

Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers

2019

Pyridine[4]arenes have previously been considered as anion binding hosts due to the electron-poor nature of the pyridine ring. Herein, we demonstrate the encapsulation of Me4N+ cations inside a dimeric hydrogen-bonded pyridine[4]arene capsule, which contradicts with earlier assumptions. The complexation of a cationic guest inside the pyridine[4]arene dimer has been detected and studied by multiple gas-phase techniques, ESI-QTOF-MS, IRMPD, and DT-IMMS experiments, as well as DFT calculations. The comparison of classical resorcinarenes with pyridinearenes by MS and NMR experiments reveals clear differences in their host–guest chemistry and implies that cation encapsulation in pyridine[4]arene…

Powerful Fluoroalkoxy Molybdenum(V) Reagent for Selective Oxidative Arene Coupling Reaction

2013

We introduce the novel fluoroalkoxy molybdenum(V) reagent 1 which has superior reactivity and selectivity in comparison to MoCl5 or the MoCl5 /TiCl4 reagent mixture in the oxidative coupling reactions of aryls. Common side reactions, such as chlorination and/or oligomer formation, are drastically diminished creating a powerful and useful reagent for oxidative coupling. Theoretical treatment of the reagent interaction with 1,2-dimethoxybenzene-type substrates indicates an inner-sphere electron transfer followed by a radical cationic reaction pathway for the oxidative-coupling process. EPR spectroscopic and electrochemical studies, X-ray analyses, computational investigations, and the experim…

Novel cationic solid-lipid nanoparticles as non-viral vectors for gene delivery.

2007

In this paper, the suitability of novel cationic solid-lipid nanoparticles (SLN) as a nonviral transfection agent for gene delivery was investigated. SLN were produced by using the microemulsion method and Compritol ATO 888 as matrix lipid, dimethyldioctadecylammonium bromide as charge carrier and Pluronic F68 as surfactant. Obtained nanoparticles were approximately 120 nm in size and positively charged, with a zeta potential value equal to +45 mV in twice-distilled water. Cationic SLN were able to form stable complexes with DNA and to protect DNA against DNase I digestion. The SLN-DNA complexes were characterized by mean diameter and zeta potential measurements. In vitro studies on human l…

Effect of blastfurnace slag addition to Portland cement for cationic exchange resins encapsulation

2013

In the nuclear industry, cement-based materials are extensively used to encapsulate spent ion exchange resins (IERs) before their final disposal in a repository. It is well known that the cement has to be carefully selected to prevent any deleterious expansion of the solidified waste form, but the reasons for this possible expansion are not clearly established. This work aims at filling the gap. The swelling pressure of IERs is first investigated as a function of ions exchange and ionic strength. It is shown that pressures of a few tenths of MPa can be produced by decreases in the ionic strength of the bulk solution, or by ion exchanges (2Na + instead of Ca 2+ , Na + instead of K + ). Then,…

Transition Metal Catalyzed Olefin, Cycloolefin, and Styrene Polymerization

2013

The sections in this article are History and Trends Polymerization Processes Supported Catalysts and Morphology Control Polymerization Mechanisms and Stereoselectivity History and Principles of Metallocene Catalysis Regio- and Stereoselective Polymerization of α-Olefins Polymerization of Cyclic Olefins, Cyclopolymerization, and Stereoselective Polymerization of Styrene Late Transition Metal Catalysts Transition Metal Catalyzed Copolymerization Acknowledgements

Synthesis of monodisperse oligomers of ɛ-aminocaproic acid up to a degree of polymerization of 25 by the Merrifield method (1)

1967

Transition metal derivatives of low oxidation state phosphorus oxoacids: synthetic pathways and structural studies

1993

Abstract A general synthetic approach intended to rationalize the solution preparative chemistry of transition metal phosphites and hypophosphites is presented. As previously shown for other derivatives containing also tetrahedral or pseudotetrahedral oxoanions, the hydrolytic processes affecting the cationic moieties play a determinant role on the very nature of the final solid. In fact, despite the limited number of donor atoms in the anions, the crystal chemistry of these compounds is quite intricate because of both the variety of possible cationic aggregates and the many ways to interconnect them through pseudotetrahedral anionic groups.

Incorporation of Pd nanoparticles in mesostructured silica

2009

Monodisperse Pd nanoparticles were prepared by controlled reduction in organic phase and subsequent transfer to aqueous phase. A systematic study was carried out to finely tune nanoparticle size and optimize particle size distribution. The use of 4-dimethylaminopyridine as a transfer agent allowed for the easy and quantitative extraction of the Pd to the aqueous phase. The quaternary amine-functionalized metal nanoparticles were then used as metallic micelle replicas to grow silica around them. This novel and facile metal incorporation method provided an excellent dispersion and homogeneity of Pd nanoparticles on silica supports. In addition, cationic surfactants, such as cetyltrimethylammo…

Effect of cationic polyamidoamine dendrimers on ionic transport through nanochannels

2021

Abstract The effect of polyamidoamine (PAMAM) dendrimers (generations G0–G3) on the ion transport properties of nanochannels (conical and cylindrical) is studied either by surface functionalization or by addition to the electrolyte solution. Surface functionalization with cationic dendrimers lead to inversion of the ion current rectification, indicating the anion selectivity of the modified nanochannels. This anion selectivity increases by immobilizing higher-generation dendrimers, as expected for an increase in the surface density of amino groups. However, compared to PAMAM G2, functionalization with PAMAM G3 results in higher cation and lower anion fluxes. Diffusion experiments of charged…