Fracture behavior of amorphous and semicrystalline blends of poly(vinylidene fluoride) and poly(methyl methacrylate)

The fracture behavior of blends of poly(vinylidene fluoride) and poly(methyl methacrylate) was investigated all over the composition range. A detailed analysis of the net stress versus crack opening displacement curves was performed. Fracture surface observations allowed statements on the process zone characteristics ahead of the crack tip. For the amorphous blends, the crack initiation energy is well related to the glass transition temperature. For the semicrystalline blends, the fracture energy is correlated with the degree of crystallinity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Generalization of the Copper to Late‐Transition‐Metal Transmetallation to Carbenes beyond N‐Heterocyclic Carbenes

Carbene transition‐metal complexes have become a prevalent family of catalysts enabling numerous organic transformations. Their facile synthetic access is a matter of great importance. To this end, the Cu^I‐NHC transfer methodology has emerged as a powerful alternative presenting attractive advantages over other methods. Herein, we report the remarkable ability of copper to transfer not only NHCs but also other types of carbenes such as abnormal NHCs (aNHCs), cyclic (alkyl)(amino)carbenes (CAACs), and mesoionic carbenes (MICs) to various transition metal precursors.     

carbo‐Naphthalene: A Polycyclic carbo‐Benzenoid Fragment of α‐Graphyne

A ring carbo‐mer of naphthalene, C₃₂Ar₈ (Ar=p‐n‐pentylphenyl), has been obtained as a stable blue chromophore, after a 19‐step synthetic route involving methods inspired from those used in the synthesis of carbo‐benzenes, or specifically devised for the present target, like a double Sonogashira‐type coupling reaction. The last step is a SnCl₂/HCl‐mediated reduction of a decaoxy‐carbo‐decalin, which is prepared through successive [8+10] macrocyclization steps. Two carbo‐benzene references are also described, C₁₈Ar₆ and o‐C₁₈Ar₄(C≡C‐SiiPr₃)₂. The carbo‐naphthalene bicycle is locally aromatic according to structural and magnetic criteria, as revealed by strong diatropic ring current effects on the deshielding of ¹H nuclei of the Ar groups and on the negative value of the DFT‐calculated NICS at the center of the C₁₈ rings (?12.8 ppm). The stability and aromaticity of this smallest fused molecular fragment of α‐graphyne allows prediction of the same properties for the carbon allotrope itself.     

Invariant values of kinetic parameters — Evaluation of fire retardancy application to the PP-APP/PER system

A method allowing the determination of the formulation leading to the best fire retardancy properties is presented in the case of intumescent systems. The method consists in the determination of invariant physicochemical parameters deduced from TG analysis: invariant activation energy and invariant preexponentiel factor. The relation between the values given by an evaluation test (LOI) and the invariant activation energy is then discussed.