Experimental Design Optimization of Acrylate—Tannin Photocurable Resins for 3D Printing of Bio-Based Porous Carbon Architectures

In this work, porous carbons were prepared by 3D printing formulations based on acrylate–tannin resins. As the properties of these carbons are highly dependent on the composition of the precursor, it is essential to understand this effect to optimise them for a given application. Thus, experimental design was applied, for the first time, to carbon 3D printing. Using a rationalised number of experiments suggested by a Scheffé mixture design, the experimental responses (the carbon yield, compressive strength, and Young’s modulus) were modelled and predicted as a function of the relative proportions of the three main resin ingredients (HDDA, PETA, and CN154CG). The results revealed that formulations containing a low proportion of HDDA and moderate amounts of PETA and CN154CG gave the best properties. Thereby, the optimised carbon structures had a compressive strength of over 5.2 MPa and a Young’s modulus of about 215 MPa. The reliability of the model was successfully validated through optimisation tests, proving the value of experimental design in developing customisable tannin-based porous carbons manufactured by stereolithography.     

Onset of thermal ripples at the interface of an evaporating liquid under a flow of inert gas

The dynamics of thermal ripples at the interface of a volatile pure liquid (C₂H₅OH) is studied experimentally and numerically. Liquid evaporates under a flow of inert gas (N₂) circulating along the interface. The evaporation rate is varied by regulating both the gas flow rate and the gas pressure. Experiments in microgravity environment allowed to identify a transition to “interfacial turbulence,” along which some particular events such as nearly periodic and possible intermittent behaviors. Direct numerical simulations have been performed, and compare qualitatively well with experimental results, offering new insights into the physical mechanisms involved. Small-scale ripples appear to arise from a secondary instability of large-scale convection cells and their motion seems to follow the corresponding large-scale surface flow. The relative role of surface tension and buoyancy in triggering these flows is assessed by comparing experiments and simulations in both microgravity and ground conditions. Qualitative features compare satisfactorily well such as typical speed and orientation of the thermal ripples, as well as spiral flow in the bulk.     

Chemistry of novolac resins. II. Reaction of model phenols with hexamethylenetetramine

It is proposed that the reactions of hexamethylenetetramine (HMTA) with 2,4-xylenol and with 2,6-xylenol occur by different pathways. The rate of reaction and the final product distribution depend on the initial xylenol : HMTA ratio and are different in the two systems. Measured by HMTA consumption, with 2,4-xylenol the reaction rate increased with increasing xylenol : HMTA ratios, whereas with 2,6-xylenol the rate of reaction decreased with increasing 2,6-xylenol : HMTA ratio. In systems which contain both 2,4- and 2,6-xylenol, a strong preference for reaction of the HMTA with the ortho site of 2,4-xylenol was noted. This preference was apparent even in mixtures in which 2,6-xylenol was present in greater amounts than 2,4-xylenol. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1389–1398, 1997     

Copper-Catalyzed Enantioselective Formation of C−CF3 Centers from β-CF3-Substituted Acrylates and Acrylonitriles

The catalytic asymmetric synthesis of β-trifluoromethylated esters or nitriles is reported. The use of an in situ formed chiral Cu−H complex allowed the enantioselective reduction of β-trifluoromethylated acrylates or acrylonitriles. The reaction proceeds smoothly affording the corresponding enantioenriched products in good to excellent yields and outstanding enantioselectivities (up to 98 % ee). The mechanism of the reaction was studied, and a plausible reaction pathway was suggested accordingly. Finally, the versatility of the products was highlighted through functional group manipulations.     

Controlled Release of a Micelle Payload via Sequential Enzymatic and Bioorthogonal Reactions in Living Systems

A bioorthogonal approach is explored to release the content of nanoparticles on demand. Exploiting our recently described click‐and‐release technology, we developed a new generation of cleavable micelles able to disassemble through a sequential enzymatic and bioorthogonal activation process. Proof‐of‐concept experiments showed that this new approach could be successfully used to deliver the substances encapsulated into micelles in living cells as well as in mice by two complementary targeted strategies.     

Hypervalent Silicon Compounds by Coordination of Diphosphine–Silanes to Gold

Coordination of ambiphilic diphosphine–silane ligands [o‐(iPr₂P)C₆H₄]₂Si(R)F (R=F, Ph, Me) to AuCl affords pentacoordinate neutral silicon compounds in which the metal atom acts as a Lewis base. X‐ray diffraction analyses, NMR spectroscopy, and DFT calculations substantiate the presence of Au→Si interactions in these complexes, which result in trigonal‐bipyramidal geometries around silicon. The presence of a single electron‐withdrawing fluorine atom is sufficient to observe coordination of the silane as a σ‐acceptor ligand, provided it is positioned trans to gold. The nature of the second substituent at silicon (R=F, Ph, Me) has very little influence on the magnitude of the Au→Si interaction, in marked contrast to N→Si adducts. According to variable‐temperature and 2D EXSY NMR experiments, the apical/equatorial positions around silicon exchange in the slow regime of the NMR timescale. The two forms, with the fluorine atom in trans or cis position to gold, were characterized spectroscopically and the activation barrier for their interconversion was estimated. The bonding and relative stability of the two isomeric structures were assessed by DFT calculations.     

A New,Simple and Versatile Strategy for the Synthesis of Short Segments of Zigzag‐Type Carbon Nanotubes

Short segments of zigzag single‐walled carbon nanotubes (SWCNTs) were obtained from a calixarene scaffold by using a completely new, simple and expedited strategy that allowed fine‐tuning of their diameters. This new approach also allows for functionalised short segments of zigzag SWCNTs to be obtained; a prerequisite towards their lengthening. These new SWCNT short segments/calixarene composites show interesting behaviour in solution. DFT analysis of these new compounds also suggests interesting photophysical behaviour. Along with the synthesis of various SWCNTs segments, this approach also constitutes a powerful tool for the construction of new, radially oriented π systems.