The Charging of Micellar Nanoparticles in Electrospray Ionization

Charging of nanoparticles through electrospray has scarcely been explored. Spherical nanometer‐sized amphiphilic block copolymer nanoparticles with diameters ranging from ～65 to ～150 nm were electrosprayed and analysed by charge detection spectrometry. Herein, we explore the charging of these micellar nano‐objects by conducting a thorough study in different solvents, including pure water, and upon the addition of “supercharging” agents. The charge (z) of micellar nanoparticles electrosprayed from water solution is compared to the Rayleigh’s limiting charge (z_R) of a charged water droplet of the same dimensions. An average ratio (z/z_R) of 0.6–0.65 is observed for the micellar macro‐ions, supporting the charge residue mechanism, where the number of charges available to the micellar macro‐ion is limited by the number of charges on the nanodroplet, which is a function of the surface tension of the solvent. Also we show the possibility of increasing the charging of micellar nanoparticles in the negative mode by adding organic bases (in particular piperidine) to water/methanol solutions.     

Microglial responses around intrinsic CNS neurons are correlated with axonal regeneration

Background  

Microglia/macrophages and lymphocytes (T-cells) accumulate around motor and primary sensory neurons that are regenerating axons but there is little or no microglial activation or T-cell accumulation around axotomised intrinsic CNS neurons, which do not normally regenerate axons. We aimed to establish whether there was an inflammatory response around the perikarya of CNS neurons that were induced to regenerate axons through a peripheral nerve graft.     

Differential Complexing by Cyclodextrin Twin-cavity Hosts

The twin-cavity cyclodextrin (1) in which the link is a dithiotrehalosyl unit, and the flexibly-linked dimer (2) were shown to distinguish between the heterocyclic guests 3 and 4 (clofazimine drug) in spite of the guests' small structural difference. Both cyclodextrin dimer hosts form 1:1 complexes with methyl orange and with 3, as shown by double reciprocal plots of UV-absorbance change and host concentration. However with 4, both host molecules formed a 2 : 1 (host : guest) complex . Since both dimer cavities are used to create this effect, it is a new type of selectivity for macrocyclic hosts.     

Synthesis of amphiphilic polyelectrolyte block copolymers using “living” radical polymerization. Application as stabilizers in emulsion polymerization

This paper describes the synthesis of amphiphilic block copolymers composed of an ionic poly(styrenesulfonate) first segment and a hydrophobic polystyrene second one, using TEMPO-mediated “living” radical polymerization. These copolymers proved to be efficient stabilizers in the emulsion polymerization of styrene.     

Electrodeposition of noble metal nanoparticles on carbon nanotubes

Noble metal nanoparticles can be electrodeposited on carbon nanotubes under potential control. The nanotube sidewalls serve both as the electrodeposition template and as the wire electrically connecting the deposited nanoparticles.     

Nitroxide-mediated miniemulsion polymerization of n-butyl acrylate: synthesis of controlled homopolymers and gradient copolymers with styrene

Controlled free-radical homopolymerization of n-butyl acrylate and its copolymerization with styrene have been studied in aqueous miniemulsion, using an acyclic β-phosphonylated nitroxide as a mediator, the N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide, also called SG1. Polymerization kinetics have been studied and characterization of the (co)polymers has been performed, demonstrating the successful synthesis of well-defined poly(n-butyl acrylate) homopolymers and poly(n-butyl acrylate-co-styrene) gradient copolymers.     

Pulsed‐laser radical polymerization and propagation kinetic parameters of some alkyl acrylates

Pulsed‐laser photoinitiated polymerization was used to determine, in toluene solution, the propagation kinetic parameters of a series of acrylates with increasing size of the alkyl side group. Transfer to monomer and to toluene did not occur significantly in our PLP conditions and our temperature range since no broadening of the MMD was observed, allowing generally to work with two inflection points. In contrast, depending on the nature of the acrylate and on the PLP conditions, transfer to polymer, and thus long chain branching, can critically interfere. Indeed, the Mark‐Houwink‐Sakurada parameters, which are used to calculate the absolute molar mass at the inflection point, strongly depend on the polymer structure and thus, should be carefully measured for each PLP sample. Although still preliminary, the results show that the k_ps measured in toluene solution present a tendency to continuously decrease when increasing the size of the side group. This observation is conflicting with the reported behaviour for PLP experiments in bulk, revealing a possible solvent effect.     

Functionalized latexes as substrates for atom transfer radical polymerization

The application of atom transfer radical polymerization (ATRP) to the homopolymerization of 2‐hydroxyethyl acrylate and 2‐(methacryloyloxy) ethyl trimethylammonium chloride at the surface of a crosslinked polystyrene latex functionalized with alkyl bromide groups is reported. Polymerization was carried out using the surface groups of the dialyzed latex as initiators. The resulting hydrophobic core, hydrophilic shell latexes, were analyzed by FTIR, ¹³C‐NMR spectroscopy, and dynamic light scattering.     

Simulation of Molecular Weight Distributions Obtained by Pulsed Laser Polymerization (PLP): New Analytical Expressions Including Intramolecular Chain Transfer to the Polymer

A new approach for the simulation of PLP (pulsed laser polymerization) is presented. This approach allows one to obtain new analytical solutions for different polymerization schemes, including either chain transfer to the monomer or intramolecular chain transfer to the polymer. The first results of the simulation of PLP experiments on n‐butyl acrylate at 20 °C and ambient pressure are presented.

MWDs simulated for PLP of n‐butyl acrylate, in bulk at 20 °C and ambient pressure using three models: the model with intramolecular chain transfer to the polymer (solid line), the model with chain transfer to monomer (dashed line), and the classical model (dotted line).     

Stopped-flow investigation of the cationic oligomerization of trans-1,3-diphenyl-1-butene initiated by trifluoromethanesulfonic acid in dichloromethane

Reaction of trans 1,3-diphenyl-1-butene (D), the trans ethylenic dimer of styrene, with trifluoromethanesulfonic acid in dichloromethane has been performed at temperatures lower than room temperature using a stopped-flow technique with real time UV-visible spectroscopic detection. The main product of the reaction was the indanic dimer of D. A transient absorption at 340 nm has een assigned to 1,3-diphenylbutylium, a model for the polystyryl cation. Other absorptions at 349 nm and 505 nm have also been observed and were assigned to an allylic cation, 1,3-diphenyl-1-buten-3-ylium, resulting from hydride abstraction from D. This species was very stable at temperatures lower than −30°C. A general mechanism was proposed based on a kinetic study of the involved reactions.