Short Alkylamines Research Articles

Macroradical enables electrical conduction in epoxy thermoset

A single material combining the unique properties of stable radical moieties with the versatility of the epoxy polymer is presented. Electrical conduction for any material is mostly achieved using metals, metal-organics, or organic conductors with extended π-orbital frameworks. However, in this combined material, intrinsic electronic conduction is enabled into the non-conjugated and amorphous epoxy thermoset. Furthermore, using the classical epoxy-amine curing ensures that only a highly crosslinked network with a rigid topology is formed. This design is a departure from other macroradicals with flexible backbones. The hole mobility of the neat macroradical epoxy thermoset is quantified to be ~3.1 × 10−6 cm2 V−1 s−1, already in the regime of traditional semiconductors. This electronic conduction can only be a result of radical-toradical hopping because the thermoset still retains active radicals after polymerization with a short alkyl amine when measured by electron spin resonance (EPR) spectroscopy. In the scientific literature, the synthesis of macroradicals using the direct approach is scarce. Herein, to obtain the novel radical epoxy monomer, a very mature yet simple amino-epoxide chemistry is employed to prepare a diglycidylamine based on 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl using the direct approach. EPR spectroscopy also reveals that the radical center remained stable even after epoxidation of the precursor. Consequently, this effort offers a change in thinking on how electronic conduction in open shell polymers operates especially on a rigid backbone and paves for a reassessment of the traditional epoxy polymer as enduring materials for frontier applications.

The effect of hydrophobic alkyl sidechains on size and solution behaviors of nanodiscs formed by alternating styrene maleamic copolymer

The development of amphipathic polymers, including various formulations of styrene-maleic acid (SMA) copolymers, has allowed the purification of increasing sizes and complexities of biological membrane protein assemblies in native nanodiscs. However, the factors determining the sizes and shapes of the resulting bio-nano particles remain unclear. Here, we show how grafting on short alkyl amine sidechains onto the polar residues leads to a broad set of nanoparticle sizes with improved solution behavior. The solubilization of lipid vesicles occurs over a wide range of pH levels and calcium concentrations, providing utility across the physiologically relevant range of solution conditions.Furthermore, the active SMA derivatives can contain strictly alternating monomers, which have inherently lower sequence polydispersity. Pronounced differences in the shapes of native nanoparticles were formed from Escherichia coli bacterial outer membrane containing PagP protein using methyl, ethyl and propylamine derivatives of styrene-maleic anhydride. In particular, the methylamine-substituted polymer forms smaller, monodispersed nanodiscs, while the longer alkyl derivatives form worm-like nanostructures. Thus the introduction of hydrophobicity onto the polar sidechains of amphipathic polymers has profound effects on morphology of native nanodisc, with shorter methyl moieties offering more uniformity and utility for structural biology studies.

Effects of alkylamine chain length on perovskite nanocrystals after washing and perovskite light-emitting diodes

Organic–inorganic hybrid lead halide perovskite nanocrystals (PeNCs) have received great attention as a light source for perovskite LEDs (PeLEDs) owing to the superior optical properties. However, PeNCs typically use octylamine (OAm) as capping ligands which have insulating properties. Exploring a desirable short alkylamine instead of OAm is required for the improvement of PeLEDs. Here, as one of the strategies to solve this issue, the effects of alkylamine chain length for optical properties of PeNCs and PeLED characteristics are investigated. Pentylamine is an optimal short alkylamine and precipitate luminescent PeNCs with high PLQY values of 90%. Importantly, pentylamine maintains a relatively high PLQY of 48% after spin-coating, due to the durability pentylamine has to ethyl acetate as a washing solvent. PeNCs capped with pentylamine also demonstrate an external quantum efficiency of over 1% with luminance of over 2000 cd cm−2, indicating that pentylamine has the potential to overcome the insulator properties of PeNC thin film.

A convenient phase transfer protocol to functionalize gold nanoparticles with short alkylamine ligands

HypothesisAqueous citrate-stabilized gold nanoparticles (Au NPs) cannot be directly transferred from water to an immiscible organic solution using short alkyl ligands. However, Au NPs can be transferred from water to a water-organic interface if chemical and mechanical inputs are used to modify the interfacial energy and interfacial area. Ligand exchange can then take place at this interface. After separating the particles from the liquids, they can be transferred to a different organic phase. ExperimentsHexane, alkylamine, and acetone were added to aqueous citrate-stabilized Au NPs to form a film at the system interfaces. After removing the liquid phases, Au NPs were readily redispersed into tetrahydrofuran (THF). The size and shape of the transferred Au NPs were evaluated by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). FindingsAu NPs with 13nm diameter are readily segregated from water with the aid of short alkylamine ligands. They form a thin film at the water/organic solvent interface, rendering them easy to separate from the liquid phases and possible to redisperse into another organic solvent. After the phase transfer process, Au NPs were functionalized with short amine ligands. In addition, the shape and size of Au NPs were preserved. The short amine-protected Au NPs in THF can stay stable for up to 27days or longer.

Crystal engineering on layered zirconium phosphonates. Crystal structure (from X-ray powder data) and non-covalent interactions on the layered zirconium compound of 4-[bis(phosphonomethyl)amino]butanoic acid

A new layered zirconium diphosphonate fluoride, ZrHF(O3PCH2)2NHC3H6CO2, has been prepared by the reaction of zirconyl chloride with 4-[bis(phosphonomethyl)amino]butanoic acid in the presence of HF. Its structure has been determined “ab initio” by X-ray powder data. It crystallizes in the monoclinic space group P21/c (No. 14), with a = 12.9640(3) A, b = 8.9900(4) A, c = 10.7924(4) A, β = 101.854(4)°, and Z = 4. Both of the phosphonic groups of each diphosphonate building block are bonded to zirconium atoms on the same side of the layers. Only one organic residue is associated with two phosphonate tetrahedra. The packing of layers creates an interdigitated arrangement of organic groups in the interlayer region. Two strong non-covalent interactions are present in the structure. One of them involves neighbouring P–OH and amino groups, while the other interaction engages terminal carboxylic groups and fluorine atoms belonging to adjacent layers. Thermal treatment at 240 °C causes the loss of one mole of HF per mole of zirconium, with the formation of a stable compound in which carboxylate groups probably coordinate to the zirconium atoms belonging to adjacent layers. Preliminary experiments of intercalation with ammonia and short alkylamines are also reported.

Catalysis of ester aminolysis by cyclodextrins. The reaction of alkylamines with p-nitrophenyl alkanoates

The effects of four cyclodextrins (alpha-CD, beta-CD, hydroxypropyl-beta-CD, and gamma-CD) on the aminolysis of p-nitrophenyl alkanoates (acetate to heptanoate) by primary amines (n-propyl to n-octyl, isobutyl, isopentyl, cyclopentyl, cyclohexyl, benzyl) in aqueous solution have been investigated. Rate constants for amine attack on the free and CD-bound esters (k(N) and k(cN)) have ratios (k(cN)/k(N)) varying from 0.08 (retardation) to 180 (catalysis). For the kinetically equivalent process of free ester reacting with CD-bound amine (k(Nc)), the ratios k(Nc)/k(N) vary from 0.2 to 28. Either way, there is evidence of catalysis in some cases and retardation in others. Changes in reactivity parameters with structure indicate more than one mode of transition state binding to the CDs. Short esters react with short alkylamines by attack of free amine on the ester bound by its aryl group, but for longer amines, free ester reacts with CD-bound amine. Reaction of long esters with long amines, which is catalyzed by beta-CD and gamma-CD, involves inclusion of the alkylamino group and possibly the ester acyl group. The larger cavity of gamma-CD may allow the inclusion of the ester aryl group, as well as the alkylamino group, in the transition state. Reaction between an ester bound to the CD by its acyl group and free amine appears not to be important.

Formation of Aqueous Colloidal Dispersions of Exfoliated γ-Zirconium Phosphate by Intercalation of Short Alkylamines

A good exfoliation of layered γ-zirconium phosphate in aqueous medium at room temperature has been obtained by intercalation of short alkylamines such as methyl-, dimethyl- and ethyl-amine. No appreciable exfoliation was observed when butylamine or longer alkylamines were intercalated, while intermediate behavior was obtained with the intercalation of propylamine. Since a good exfoliation of this layered compound is an essential step for its functionalization by topochemical reactions with phosphonic or phosphinic acids, the amine intercalation compounds and the various steps of the intercalation processes were investigated in order to obtain information on the mechanism of the exfoliation and a model of this mechanism is proposed. The use of the colloidal dispersion of exfoliated lamellae for the preparation of auto-consistent and flexible membranes as well as thin supported films of γ-zirconium phosphate is described.

2‘-O-Aminopropyl Ribonucleotides: A Zwitterionic Modification That Enhances the Exonuclease Resistance and Biological Activity of Antisense Oligonucleotides

Oligonucleotides containing 2'-O-aminopropyl-substituted RNA have been synthesized. The 2'-O-(aminopropyl)adenosine (APA), 2'-O-(aminopropyl)cytidine (APC), 2'-O-(aminopropyl)-guanosine (APG), and 2'-O-(aminopropyl)uridine (APU) have been prepared in high yield from the ribonucleoside, protected, and incorporated into an oligonucleotide using conventional phosphoramidite chemistry. Molecular dynamics studies of a dinucleotide in water demonstrates that a short alkylamine located off the 2'-oxygen of ribonucleotides alters the sugar pucker of the nucleoside but does not form a tight ion pair with the proximate phosphate. A 5-mer with the sequence ACTUC has been characterized using NMR. As predicted from the modeling results, the sugar pucker of the APU moiety is shifted toward a C3'-endo geometry. In addition, the primary amine rotates freely and is not bound electrostatically to any phosphate group, as evidenced by the different sign of the NOE between sugar proton resonances and the signals from the propylamine chain. Incorporation of aminopropyl nucleoside residues into point-substituted and fully modified oligomers does not decrease the affinity for complementary RNA compared to 2'-O-alkyl substituents of the same length. However, two APU residues placed at the 3'-terminus of an oligomer gives a 100-fold increase in resistance to exonuclease degradation, which is greater than observed for phosphorothioate oligomers. These structural and biophysical characteristics make the 2'-O-aminopropyl group a leading choice for incorporation into antisense therapeutics. A 20-mer phosphorothioate oligonucleotide capped with two phosphodiester aminopropyl nucleotides targeted against C-raf mRNA has been transfected into cells via electroporation. This oligonucleotide has 5-10-fold greater activity than the control phosphorothioate for reducing the abundance of C-raf mRNA and protein.