Number Of Ammonium Groups Research Articles

Synthesis of size-controlled carbon microspheres from resorcinol/formaldehyde for high electrochemical performance

Nanostructured phenolic resin-based carbon aerogels with an extensive network structure are regarded as ideal energy storage materials for supercapacitors. However, the initial bulk form and low capacitance of previously reported porous carbon aerogels are problematic for practical use. Phenolic resin-based porous carbon spheres were synthesized by a simple hydrothermal process using ammonia, ethylenediamine or hexylenediamine as a catalyst. The porous carbon spheres were investigated by SEM, BET, XPS, etc. It was found that the number of ammonium groups, length of the alkyl chain and processing temperature play vital roles in determining the pore structure, size and uniformity of the carbon spheres. NH4+ is necessary to obtain the carbon spheres and but changing the other parameters has no obvious effect on their crystal structure. The sample prepared at a hydrothermal temperature of 80 °C using ammonia as the catalyst has the highest specific capacitance of 233.8 F g−1 at a current density of 1.0 A g−1. It has an excellent capacitance retention of 98% after 10,000 charge/discharge cycles at 7 A g−1, indicating its good cycling stability and rate capability. This result shows that a higher specific surface area, porosity and defect density are probably the crucial factors in improving the electrochemical capacitance.

Anion conductive aromatic polymers containing fluorenyl groups: Effect of the position and number of ammonium groups

ABSTRACTSynthesis and properties of anion conductive aromatic block copolymers, QPE‐bl‐3, QPE‐bl‐3 M2, and M4, containing fluorenylidene biphenylene groups as scaffold for ammonium groups are described. These copolymers share the same main chain structure, but the position and the number of ammonium groups on a fluorenyl group differ. High molecular weight quaternized block copolymers were obtained via typical chloromethylation reaction or using preaminated monomers, and were well‐characterized by 1H NMR spectra. Self‐standing bendable membranes were obtained by solution casting. QPE‐bl‐3 M4 membranes containing four ammonium groups per hydrophilic repeat unit (highest ammonium density) in the hydrophilic block exhibited well developed phase‐separated morphology, while QPE‐bl‐3 membranes containing two ammonium groups per hydrophilic repeat unit exhibited high anion conductivity. The highest anion conductivity (104 mS/cm) was obtained with QPE‐bl‐3 membrane (IEC = 2.1 meq/g) at 80 °C in water. An H2/O2 alkaline fuel cell was operable with the membrane to achieve 62 mW/cm2 of the maximum power density at 161 mA/cm2 of the current density. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 935–944

A new polymorphic form of Otilonium Bromide

"Otilonium bromide (C29H43 N2 O4+.Br-) is a quaternary ammonium derivative which has been proven a potent spasmolytic drug with a good tolerability profile, used in the treatment of irritable bowel syndrome. We present herein the structural analysis of an unreported polymorphic form (I), comparing with the only one known so far and already reported [1] polymorphic form of the compound (II). The data set for I was obtained from a twinned specimen. The poor quality of the data thus available did not pose any problem in the structure resolution, but it did instead in refinement: the alkyloxy chains and ethyl branches in the quaternary ammonium groups needed some continuity restraints in their anisotropic displacement factors. In form II this effect appeared enhanced, ending up in unusually large anisotropic displacement parameters for most atoms in the chain. The main points of molecular disagreement reside in the torsion angles where the alkyloxy chains and quaternary ammonium groups leave the planar mainframe. The only notorious intermolecular contacts in both structures appear to be a number of rather weak C–H···Br ones involving the quaternary ammonium groups somehow ""wrapping"" the bromide counterion. There are a few C–H···O contacts interlinking molecules to each other. The phase transformation occurs at 124(2)°C and can be followed by DSC and XRPD. A detailed analysis shows some features in common, viz., in both structures packing stability is mainly due to the ionic interaction between the N+ and the Br-, with the latter ion being evenly surrounded by a number of ammonium groups in a way that they define regular 2D arrays "sandwiching" the neutral part of the molecules, which thus act as spacers. These similarities allow giving a plausibility argument about the way in which the transition may take place."

Molecular Recognition of Protonated Polyamines at Calix[4]Crown-5 Self-Assembled Monolayer Modified Electrodes by Impedance Measurements

Molecular recognition of protonated aliphatic polyamines has been studied at calix[4]crown-5 self-assembled monolayer modified gold electrodes by electrochemical impedance spectroscopic (EIS) experiments. The energy of complex formation between the calix [4]crown-5 molecule and a series of alkyl ammonium ions was shown by molecular modeling and EIS experiments to depend on the number of amine groups in the alkyl chain as well as the number of methylene groups between the amine groups. The structures of complexes formed between the crown ether on the lower rim of calix[4]arene and protonated amines were determined by minimizing the complex formation energies. The adducts thus formed on the SAM rendered the electron transfer from the electrode to the probe (Fe(CN)63-/4- pair) easier or more difficult depending on the number of ammonium groups and their arrangement in linear alkyl chains. Analytical procedures have been developed to detect protonated spermidine (a recognized cancer marker) in simulated urine, blood, erythrocyte, and cerebrospinal fluids.

Polymeric Sorbents for Bile Acids. 5. Polyacrylamide Resins with Ammonium-Containing Pendants

Isotherms have been determined for the sorption of bile salt anions, generally glychocolate (GCA - ), in Tris buffer by cross-linked polyacrylamide resins with ammonium-containing pendent groups having the general structure of P-{(CH 2 ) n N + R 2 Cl - }mR, where R is H or a CH 3 group, and n and m are integers in the range of 2-12 and 1-3, respectively. The sorption capacity increases with the number of ammonium groups per pendant, in accord with the primary importance of electrostatic interactions. In general, the binding affinity of the resins for GCA - also increases with an increase in the hydrophobicity of the pendants. The isotherms for the binding of GCA - by the resins with long hydrophobic spacers have a normal Langmuir shape, while a distinct S-shape is observed for the sorption by resins with shorter spacers. The S-shaped isotherms indicate a positive cooperativity in the binding, probably due to hydrophobic interactions and H-bonding among bile salt anions bound at adjacent positions within the resin beads. On the basis of the sorption characteristics, it is proposed that the binding is accompanied by the development of a considerable degree of order within the beads, involving either the formation of pendent group-bile salt anion reversed mixed micelles or conventional micelles, depending on pendant structure. The resins with C 12 spacers exhibit binding properties that are significantly superior to those of cholestyramine, the bile acid sequestrant currently used clinically for the treatment of hypercholesterolemia.