University of Mons

About: University of Mons is a education organization based out in Mons, Belgium. It is known for research contribution in the topics: Large Hadron Collider & Standard Model. The organization has 3073 authors who have published 9465 publications receiving 294776 citations.

Synthesis of Allylamine Plasma Polymer Films: Correlation between Plasma Diagnostic and Film Characteristics

Abstract: Primary amine-based plasma polymer films (NH 2 -PPF) were synthesized using plasma polymerization of allylamine in continuous wave (CW) and pulsed radio-frequency (RF) modes. Plasma chemistry, studied by residual gas analysis mass spectrometry, revealed that the precursor fragmentation is a function of the equivalent power (P eq ) dissipated in the discharge, independently of the plasma mode used. X-ray photoelectron spectroscopy combined with time-of-flight secondary ion mass spectrometry suggests as the precursor fragmentation in the plasma increases: (i) a decrease of the primary amine concentration in the NH 2 -PPF (%NH 2 ) and (ii) an increase of the cross-linking degree. For a given P eq , similar to the precursor fragmentation in the plasma, the NH 2 -PPF characteristics were found to be independent of the plasma mode used. Therefore, the main advantage of using pulsed RF processes over CW ones is the possibility to work at very low P eq which enables low precursor fragmentation, optimization of %NH 2 , and reduction of the film cross-linking degree. The chemical composition and the cross-linking degree of the NH 2 -PPF synthesized by allylamine plasma polymerization can thus be tailored by adjusting the equivalent RF power injected in the plasma.

Stereocomplexation of Polylactide Enhanced by Poly(methyl methacrylate): Improved Processability and Thermomechanical Properties of Stereocomplexable Polylactide-Based Materials

Abstract: Stereocomplexable polylactides (PLAs) with improved processability and thermomechanical properties have been prepared by one-step melt blending of high-molecular-weight poly(l-lactide) (PLLA), poly(d-lactide) (PDLA), and poly(methyl methacrylate) (PMMA). Crystallization of PLA stereocomplexes occurred during cooling from the melt, and, surprisingly, PMMA enhanced the amount of stereocomplex formation, especially with the addition of 30-40 % PMMA. The prepared ternary blends were found to be miscible, and such miscibility is likely a key factor to the role of PMMA in enhancing stereocomplexation. In addition, the incorporation of PMMA during compounding substantially raised the melt viscosity at 230 °C. Therefore, to some extent, the use of PMMA could also overcome processing difficulties associated with low viscosities of stereocomplexable PLA-based materials. Semicrystalline miscible blends with good transparency were recovered after injection molding, and in a first approach, the thermomechanical properties could be tuned by the PMMA content. Superior storage modulus and thermal resistance to deformation were thereby found for semicrystalline ternary blends compared to binary PLLA/PMMA blends. The amount of PLA stereocomplexes could be significantly increased with an additional thermal treatment, without compromising transparency. This could result in a remarkable thermal resistance to deformation at much higher temperatures than with conventional PLA. Consequently, stereocomplex crystallization into miscible PLLA/PDLA/PMMA blends represents a relevant approach to developing transparent, heat-resistant, and partly biobased polymers using conventional injection-molding processes.

Theoretical Lifetimes and Oscillator Strengths in Ce II. Application to the Chemical Composition of the Sun

Abstract: A new set of transition probabilities is derived for many transitions of Ce II of astrophysical interest. A relativistic Hartree-Fock method, combined with a least-squares fitting of the available experimental levels, including a number of newly determined values, has been used for the determination of the eigenfunctions and eigenvalues. Configuration interaction and core-polarization effects have been introduced in the calculations. The derived oscillator strengths lead to a new value of the cerium abundance in the solar photosphere, ACe = 1.70 ± 0.04 (in the usual logarithmic scale) which is somewhat larger but in reasonable agreement with the meteoritic result.

Rotator side chains trigger cooperative transition for shape and function memory effect in organic semiconductors.

Abstract: Martensitic transition is a solid-state phase transition involving cooperative movement of atoms, mostly studied in metallurgy. The main characteristics are low transition barrier, ultrafast kinetics, and structural reversibility. They are rarely observed in molecular crystals, and hence the origin and mechanism are largely unexplored. Here we report the discovery of martensitic transition in single crystals of two different organic semiconductors. In situ microscopy, single-crystal X-ray diffraction, Raman and nuclear magnetic resonance spectroscopy, and molecular simulations combined indicate that the rotating bulky side chains trigger cooperative transition. Cooperativity enables shape memory effect in single crystals and function memory effect in thin film transistors. We establish a molecular design rule to trigger martensitic transition in organic semiconductors, showing promise for designing next-generation smart multifunctional materials.

Synthesis of Nitrogen‐Doped ZigZag‐Edge Peripheries: Dibenzo‐9a‐azaphenalene as Repeating Unit

Abstract: A bottom-up approach toward stable and monodisperse segments of graphenes with a nitrogen-doped zigzag edge is introduced. Exemplified by the so far unprecedented dibenzo-9a-azaphenalene (DBAPhen) as the core unit, a versatile synthetic concept is introduced that leads to nitrogen-doped zigzag nanographenes and graphene nanoribbons.