Investigating the effect of randomly methylated β-cyclodextrin/block copolymer molar ratio on the template-directed preparation of mesoporous alumina with tailored porosity

Supramolecular assemblies formed between cyclodextrins and block copolymers can be efficiently used as templates for the preparation of mesoporous materials with controlled porosity. In this work, we use dynamic light scattering (DLS) and viscosity measurements to follow the variations occurring in the size and morphology of the triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (P123) micelles in the presence of various amounts of randomly methylated β-cyclodextrin (RAMEB). The results obtained with a series of solution compositions reveal that the cyclodextrin-to-copolymer (RAMEB/P123) molar ratio plays a crucial role in the growth rate of the micelles. At low RAMEB/P123 molar ratios (below ~7.5), a swelling effect of the cyclodextrin in the P123 micelles is noticed together with a modification of the micellar curvature from spherical to ellipsoidal. At high molar ratios (~7.5 and above), an abrupt transition toward large supramolecular assemblies, which no longer resemble micelles, occurs. When the RAMEB-swollen P123 micelles are used as templates to direct the self-assembly of colloidal boehmite nanoparticles, mesoporous γ-Al₂O₃ materials with high surface areas (360–400 m²/g), tunable pore sizes (10–20 nm), large pore volumes (1.3–2.0 cm³/g) and fiberlike morphologies are obtained under mild conditions. The composition of the mixed micellar solution, in particular the cyclodextrin-to-copolymer molar ratio, appears to be a key factor in controlling the porosity of alumina.     

Gallium‐Assisted Transfer Hydrogenation of Alkenes

We report a rare case of alkene transfer hydrogenation using a main‐group compound instead of a transition‐metal complex as catalyst. We disclosed that 1,4‐cyclohexadiene can be used as H₂ surrogate towards olefin reduction in the presence of [IPrGaCl₂][SbF₆]. Hydrogenative cyclizations have also been carried out because this cationic gallium complex is also a potent hydroarylation catalyst.     

Reactivity of cyclohexene epoxides toward intramolecular acid-catalyzed cyclizations for the synthesis of naturally occurring cage architectures

This account compiles our results on the reactivity of cyclohexene epoxides toward the synthesis of naturally occurring cage architectures, in particular, the one found in harringtonolide. Bicyclic and branched monocyclic functional triads (hydroxy-epoxy-esters) were synthesized with the aim of undertaking cascade processes toward the formation of lactone and/or cycloether bridges, through a central epoxide opening. This work successfully culminated in the cascade cyclization of the fully oxygenated bridge-structure of harringtonolide, by using a dual Brønsted-Lewis acid complex.     

Enantioenriched Methylene‐Bridged Benzazocanes Synthesis by Organocatalytic and Superacid Activations

Achieving in a straightforward way the synthesis of enantioenriched elaborated three‐dimensional molecules related to bioactive natural products remains a long‐standing quest in organic synthesis. Enantioselective organocatalysis potentially offers a unique opportunity to solve this problem, especially when combined with complementary modes of activation. Here, we report the sequential association of organocatalytic and superacid activations of simple linear achiral readily available precursors to promote the formation of unique highly elaborated chiral methylene‐bridged benzazocanes exhibiting three to five fully‐controlled stereocenters. This peculiar backbone, difficult to assemble by standard synthetic approaches, is closely related to bioactive natural and synthetic morphinans and benzomorphans. The formation of a highly reactive chiral 7‐membered ring N‐acyl iminium superelectrophilic ion, evidenced by low‐temperature in situ NMR experiments, triggers a challenging stereoselective Friedel–Crafts‐type cyclization.     

Lattice Boltzmann Solid Particles in a Lattice Boltzmann Fluid

We define a lattice Boltzmann model of solid, deformable suspensions immersed in a fluid itself described in terms of the lattice Boltzmann method. We discuss the rules governing the internal dynamics of the solid object as well as the rules specifying the interaction between solid and fluid particle. We perform a numerical drag experiment to validate the model. Finally we consider the case of a population of flexible chains in suspension in a shear stress flow and study the influence on the velocity profile.     

Induction heating for surface triggering styrene polymerization on titanium modified with ATRP initiator

Titanium and its alloys present high interests for technological applications due to their high corrosion resistance, mechanical properties and biocompatibility. In combination with these remarkable characteristics, some Ti applications require specific surface properties that can be imparted with suitable surface functionalizations of the TiO(2) oxide layer. The present work aims to study the surface-initiated ATR polymerization of styrene on titanium substrates, using grafted 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid as initiator and to compare the impact of two different heating ways on the efficiency of this polymerization: induction vs. conventional heating. The ability of the initiator to bind titanium substrates and act as an initiator for ATRP of styrene is investigated: both heating conditions led to the polymerization of styrene on modified titanium substrates. However, induction heating appeared to be much more efficient than conventional heating, leading to the formation of a thicker, much denser polystyrene layer than conventional heating after only 1h of polymerization.     

Surface-initiated ATRP of 2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate on Phynox

Phynox is of high interest for technological applications due to its high corrosion resistance, mechanical properties and biocompatibility. In combination with these remarkable characteristics, some Phynox applications require specific surface properties that can be imparted with suitable surface functionalizations of the oxide layer. The present work aims at studying the surface-initiated atom transfer radical polymerization (ATRP) of 2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate (MPC) on Phynox substrates, using grafted 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid as initiator. The ability of the initiator to bind Phynox substrates and act as an initiator for ATRP of MPC is investigated. It appears that ATRP polymerization of MPC on modified Phynox substrates already takes place in aqueous media at room temperature, but the yield at 90 °C is superior.     

Positive Cooperative Effect in Ion-Pair Recognition by a Tris-urea Hemicryptophane Cage

The synthesis of a hemicryptophane cage combining a CTV unit with a C₃ symmetrical moiety bearing three urea functions is reported. This host was found to bind anions with higher binding constants than other previously reported hemicryptophanes. Due to its heteroditopic character this cage proved to be an efficient ion-pair receptor. The best cooperativity effect was observed for the tetramethylammonium bromide (TMABr) salt, which was confirmed and rationalized by DFT calculations.     

Magnesium promoted autocatalytic dehydrogenation of amine borane complexes: A reliable,non-cryogenic,scalable access to boronic acids

Owing to the unusual reactivity of dialkylamine-borane complexes, a methodology was developed to simply access boronic acids. The intrinsic instability of magnesium aminoborohydride was tweaked into a tandem dehydrogenation borylation sequence. Proceeding via an autocatalytic cycle, amineborane dehydrogenation was induced by a variety of Grignard reagents. Overall, addition of the organomagnesium species onto specially designed dialkylamine-borane complexes led to a variety of boronic acids in high yields. In addition, the reaction can be performed under Barbier conditions, on a large scale.     

Advances in multi-domain lattice Boltzmann grid refinement

Grid refinement has been addressed by different authors in the lattice Boltzmann method community. The information communication and reconstruction on grid transitions is of crucial importance from the accuracy and numerical stability point of view. While a decimation is performed when going from the fine to the coarse grid, a reconstruction must performed to pass form the coarse to the fine grid. In this context, we introduce a decimation technique for the copy from the fine to the coarse grid based on a filtering operation. We show this operation to be extremely important, because a simple copy of the information is not sufficient to guarantee the stability of the numerical scheme at high Reynolds numbers. Then we demonstrate that to reconstruct the information, a local cubic interpolation scheme is mandatory in order to get a precision compatible with the order of accuracy of the lattice Boltzmann method.These two fundamental extra-steps are validated on two classical 2D benchmarks, the 2D circular cylinder and the 2D dipole–wall collision. The latter is especially challenging from the numerical point of view since we allow strong gradients to cross the refinement interfaces at a relatively high Reynolds number of 5000. A very good agreement is found between the single grid and the refined grid cases.The proposed grid refinement strategy has been implemented in the parallel open-source library Palabos.