Thermal and radical polymerization of anthracene acrylates and methacrylates

The thermal and radical-induced polymerizations of 9-anthrylmethyl acrylate ( I ), 9-anthrylmethyl methacrylate ( II ), 1′-(9-anthryl)ethyl acrylate ( III ), and 1′-(9-anthryl)ethyl methacrylate ( IV ) have been studied. It was found that the radical-induced polymerization takes place for the methacrylates only, while thermal polymerization leads to polymers for both types of monomers and takes place by Diels–Alder cycloaddition in the case of acrylates, and by both normal enchainment and Diels–Alder cycloaddition in the case of methacrylates.     

On an integral operator

In this paper we derive some criteria for univalence of a general integral operator for analytic functions in the open unit disk.     

Two-step, one-pot Ni-catalyzed neopentylglycolborylation and complementary Pd/Ni-catalyzed cross-coupling with aryl halides, mesylates, and tosylates

Two-step, one-pot neopentylglycolborylation of aryl iodides and bromides catalyzed by NiCl2(dppe) and NiCl2(dppp) is reported. Electron-rich and electron-deficient aryl neopentylglycolboronates were efficiently cross-coupled with aryl iodides, bromides, chlorides, mesylates, and tosylates by exploiting complementary Pd/Ni and Ni/Ni catalysis. The borylation route was further extended to a three-step, one-pot synthesis of biaryls via in situ Ni-catalyzed borylation and Pd-mediated cross-coupling.     

Thixotropic twin-dendritic organogelators

Twin-dendritic organogelators have been prepared through selective functionalization of N-(3-aminopropyl)-1,3-propanediamine (APPDA) with self-assembling dendrons by using 1,1'-carbonyldiimidazole (CDI). Subsequent modification of the APPDA linker provided an additional degree of structural diversity by which to tailor the gelator self-assembly in bulk or in the gel state. These compounds are able to gel cyclohexane, toluene, n-butyl acetate, ethyl acetate, dichloromethane, and tetrahydrofuran. 3,4-Disubstituted apical branching units provided the most efficient organogelators and show a propensity to form thixotropic gels, wherein the gel recovers its elasticity after being subjected to shear. Structural and retrostructural analysis of the twin-dendritic organogelators reveals the bulk structural characteristics to be indicative of the subsequent gel properties. Diverse self-organized arrays were identified in bulk and all are able to form gels, thus indicating the role of quasiequivalence in mediating self-assembly in the gel state. Furthermore, we have found that porous columnar mesophases provide a strategy by which to prepare thixotropic gels. We demonstrate the importance of weak lateral hydrogen bonding within a column stratum versus hydrogen bonding along the length of the column for forming porous columnar mesophases and, by extension, thixotropic gels.     

Degradation of γ-irradiated linear perfluoroalkanes at high dosage

The effects of the carbon backbone chain length on the EPR spectra of linear perfluoro-n-alkanes (PFAs) γ-irradiated at 77 K was studied for the short chain n-C₆F₁₄, n-C₈F₁₆, n-C₁₂F₂₆, and n-C₁₆F₃₄ molecules as well as the polymer polytetrafluoroethylene (PTFE). The experimental data show that the processes occurring during radiolysis of perfluoro-n-alkanes and polytetrafluoroethylene are very similar. EPR spectra of irradiated perfluoro-n-alkanes at low radiation dose show superimposed signals from three radicals: -F₂CCFCF₂-, -CF₂CF₂ and F₃C. The signal intensity decreases with perfluoro-n-alkanes chain length. At doses above 2.0 MGy, a constant increase in concentration of the radicals -F₂CCFCF₂- and -CF₂CF₂ is observed with decreasing chain length. The concentration of these radicals formed during radiolysis of PFA is described by the ratio: [-CF₂CF₂]/[-F₂CCFCF₂-] ≈3/(n − 2), where n is the number of carbon atoms in the linear perfluoroalkanes. Density functional theory was used to calculate the structures of the radicals and C-F bond energies in model perfluoro-n-alkanes as well as the EPR spectra of the associated radicals. This data is used to provide further insight into the radiation stability of PTFE. Four topographical structures of polytetrafluoroethylene, one amorphous and three crystalline, were identified by thermomechanical analysis. In the crystal phase, γ-irradiation results in their transformation to the amorphous form. The helical structure of individual perfluroalkanes readily distorts on removal of a fluorine and this will have an impact on the overall structure of the material. Such structural reorganization can lead to loss of the mechanical stability of polytetrafluoroethylene.