Structure/reactivity/photoinitiation ability relationships in novel benzo pyrazolo (or imidazo) isoquinolinone derivatives upon visible light LEDs

Isoquinolinone derivatives bearing amino‐ or nitro‐ substituent (IQNs) have been synthesized as photoinitiators and combined with various additives (i.e., iodonium salt, N‐vinylcarbazole, amine or 2,4,6‐tris(trichloromethyl)?1,3,5‐triazine) to initiate ring‐opening cationic polymerizations (CP) or free radical polymerizations under exposure to visible LEDs (e.g., LEDs at 405 nm or 455 nm, or cold white LED) or a halogen lamp. Compared to the well‐known camphorquinone‐based systems, the novel IQNs‐based combinations employed here demonstrate higher efficiencies for the CP of epoxides. The photochemically generated reactive species (i.e., cations and radicals) from the IQNs‐based systems have been investigated by steady state photolysis, cyclic voltammetry, fluorescence, laser flash photolysis, and electron spin resonance spin trapping techniques. The structure/reactivity/photoinitiating ability relationships of IQNs‐based combinations are also discussed; the crucial role of the excited state lifetimes of the photoinitiators to ensure efficient quenching by additives is clearly underlined. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1806–1815     

Naphthalic anhydride derivatives: Structural effects on their initiating abilities in radical and/or cationic photopolymerizations under visible light

Only one naphthalic anhydride derivative has been reported as light sensitive photoinitiator, this prompted us to further explore the possibility to prepare a new family of photoinitiators based on this scaffold. Therefore, eight naphthalic Naphthalic anhydride derivatives (ANH1‐ANH8) have been prepared and combined with an iodonium salt (and optionally N‐vinylcarbazole) or an amine (and optionally 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine) to initiate the cationic polymerization of epoxides and the free radical polymerization of acrylates under different irradiation sources, that is, very soft halogen lamp (～ 12 mW cm^?2), laser diode at 405 nm (～1.5 mW cm^?2) or blue LED centered at 455 nm (80 mW cm^?2). The ANH6 based photoinitiating systems are particularly efficient for the cationic and the radical photopolymerizations, and even better than that of the well‐known camphorquinone based systems. The photochemical mechanisms associated with the chemical structure/photopolymerization efficiency relationships are studied by steady state photolysis, fluorescence, cyclic voltammetry, laser flash photolysis, and electron spin resonance spin‐trapping techniques. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2860–2866     

Use of a simple surface-active initiator in controlled/living free-radical miniemulsion polymerization under AGET and ARGET ATRP conditions

This communication describes the first example of the efficient use of a simple amphiphilic molecule as both a surfactant and an initiator in the miniemulsion polymerization of methyl methacrylate under AGET and ARGET ATRP conditions.     

Elaboration of monodisperse spherical hollow particles with ordered mesoporous silica shells via dual latex/surfactant templating: radial orientation of mesopore channels

Monodisperse spherical hollow nanoparticles of mesoporous silica featuring mesopores with a radial orientation in the silica shell were synthesized via a dual-templating method. Specifically designed polystyrene latexes with anionic or cationic surface charges acted as the core templates, while cetyltrimethylammonium bromide served as a co-template to structure the mesopore formation during tetraethoxysilane hydrolysis/condensation. The particles were well-separated and presented homogeneous mesoporous silica shells. Average particle diameters were less than 200 nm, and the particles displayed high values of specific surface area and pore volume. The shell thickness and the hollow core diameter could be tuned independently while the radial pore structure was preserved. A detailed analysis of the nitrogen adsorption-desorption isotherms proved that the central cavity was completely isolated from the external medium, that is, only accessible through the radial mesopores of the shell. Consequently, our particles gather the advantages of a well-defined structure, straight penetrating channels across the silica shell, and a high accessible porous volume of the central core. These properties make them far better candidates than simple mesoporous particles for any storage and/or controlled release applications.     

Supercritical fluid chromatography and two-dimensional supercritical fluid chromatography of polar car lubricant additives with neat CO(2) as mobile phase

Car lubricant additives are added to mineral or synthetic base stocks to improve viscosity and resistance to oxidation of the lubricant and to limit wear of engines. Their total amount in the commercial lubricant varies from a few percents to 20-25%. As they belong to various chemical classes and are added to a very complex medium, the base stock, their detailed chromatographic analysis is very difficult and time consuming as it should involve sample treatment and preparative scale separations in order to simplify the sample. The aim of this work is to determine the feasibility of the separation of low molecular weight lubricant additives using various packed columns with pure CO(2) as a mobile phase to enable implementation of flame ionisation detection as universal detector. This is part of a hypernated system including more sophisticated specific detectors, such as AED, FTIR or MS to obtain detailed structural information of compounds. This paper is devoted to the comparison of some stationary phases supposed to provide hydrocarbon group type separation (silica and normal phase) or separations on alkyl-bonded silica in non-aqueous mode of some selected classes of additives in test mixtures or in base stocks. Adsorption chromatography allows partial separation of additives from the base stocks while the direct elution of test additives can only be obtained on reversed phase supports having a very efficient silanol group protection so the interaction of the more polar compounds is much reduced. A two-dimensional scheme of analysis is also described. It combines adsorption chromatography to separate most of the polar additives from the base stock and alkyl-bonded silica for more detailed separation of the additives. However, overlapping between groups of compounds and the lack of resolution between some additives and the base stock should be addressed by the implementing of selective detectors.     

End‐Group Characterization of Poly(acrylic acid) Prepared by Nitroxide‐Mediated Controlled Free‐Radical Polymerization

Summary: A low‐molar‐mass poly(acrylic acid) with a narrow molar‐mass distribution, prepared by SG1 nitroxide‐mediated controlled free‐radical polymerization, was subjected to end‐group analysis to confirm its living nature. ¹H and ³¹P NMR spectroscopy confirmed the presence of the SG1‐based alkoxyamine end group. Furthermore, chain extension with styrene and n‐butyl acrylate demonstrated the ability of the homopolymer to initiate the polymerization of a second block. These results open the door to the synthesis of poly(acrylic acid)‐based block copolymers by direct nitroxide‐mediated polymerization of acrylic acid.

Acrylic acid polymerization using an alkoxyamine initiator based on SG1 (N‐tert‐butyl‐N‐(1‐diethyl phosphono‐2,2‐dimethylpropyl) nitroxide resulting in a homopolymer capable of initiating the polymerization of a second block.     

Asymptotic Analysis of the Stresses in Thin Elastic Shells

. In this paper, we identify the limiting stress tensor of a thin elastic shell whose thickness approaches zero. In the linear case, we use a convergence result established for the displacement field in order to get the convergence of the contravariant components of the linearised stress tensor. In the nonlinear case, the identification of the first Piola‐Kirchhoff stress tensor is made through a formal asymptotic analysis. In both cases, we show that these limiting stress fields depend on the geometry of the shell and on the boundary conditions. (Accepted June 1, 1998)     

Model kinetic study of TiCl4-induced ionization of polyisobutene capped with diphenylethylene application to the synthesis of block copolymers

The use of non-homopolymerizable monomers such as 1,1-diphenylethylene (DPE) in the synthesis of functional polymers and block copolymers by cationic polymerization has been recently reported. The most important parameters in this process, the kinetics and extent of ionization and capping as well as the stability of the cation, were investigated by studying the reaction with TiCl₄ of 1-methoxy-1,1-diphenyl-3,3,5,5-tetramethylhexane, a model for DPE-capped polyisobutene chain-end. This study was performed using ¹H NMR and the high-purity stopped-flow device coupled with UV-visible spectroscopy.     

[Mo12S12O12(OH)12(H2O)6]: A Cyclic Molecular Cluster Based on the [Mo2S2O2]2+ Building Block

The pH-dependent self-condensation of the [Mo ₂ S ₂ O ₂ ] ²⁺ complex fragment gives the wheellike Mo₁₂ cluster depicted on the right (ball-and-stick model; large balls: S, medium balls: O, small balls: Mo). Applying this synthetic strategy to other starting materials could provide access to other polyoxothiometalates with well-defined cavities.