The direct arylation polycondensation (DArP) has become one of the most important methods to construct conjugated polymers (CPs). However, the homocoupling side-reactions of aryl halides and the low regioseletive reactivities of unfunctionalized aryls hinder the development of DArP. Here, an efficient Pd and Cu co-catalyzed DArP was developed via inert C−S bond cleavage of aryl thioethers, of which robustness was exemplified by over twenty conjugated polymers (CPs), including copolymers, homopolymers, and random polymers. The capture of oxidative addition intermediate together with experimental and theoretic results suggested the important role of palladium (Pd) and copper (Cu) co-catalysis with a bicyclic mechanism. The studies of NMR, molecular weights, trap densities, two-dimensional grazing-incidence wide-angle X-ray scattering (2D-GIWAXS), and the charge transport mobilities revealed that the homocoupling reactions were significantly suppressed with high regioselectivity of unfunctionalized aryls, suggesting this method is an excellent choice for synthesizing high performance CPs. 相似文献
In this paper, we discuss the special diffusive hematopoiesis model
with Neumann boundary condition. Sufficient conditions are provided for the global attractivity and oscillation of the equilibrium
for Eq. (*), by using a new theorem we stated and proved. When P(t, χ) does not depend on a spatial variable χ ∈ Ω, these results are also true and extend or complement existing results. Finally, existence and stability of the Hopf
bifurcation for Eq. (*) are studied.
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Let's twist again! Remarkable broad and twisted ribbons were generated from the self‐assembly of oligo(p‐ phenylene ethylene) (OPE) bearing dimeric deoxycholic acid pendant groups (see graphic). Varying the bile acid led to nanostructures with drastically different morphologies. The distinctive aggregate shapes of these steroid–OPE conjugates are attributed to the subtle differences in their molecular structures.
The electrochemical reduction process of trivalent Cr in the presence of formic acid is studied. The compositions of Cr complexes in electrolytes and products on cathode are investigated using ultraviolet–visible absorption spectroscopy (UV–Vis) and X-ray photoelectron spectroscopy (XPS), respectively. The geometric structures of the original and transition state ions during the electroreduction process are optimized, using density functional theory with General Gradient Approximation/Perdew-Wang 91 (GGA/PW91) calculation. The trivalent Cr primarily exists in the form of [Cr(H2O)6]3+ in the solution. [Cr(H2O)6]3+ exhibits regular-octahedron structure which is unfavorable for center Cr3+ to contact cathodic electrons. In the presence of formic acid, formate ion promotes the formation of the reactive intermediate, [Cr(H2O)4CHOO]2+, which possesses irregular-octahedron structure with Cr3+ ion as a vertex. In this case, Cr3+ ion can contact the cathode and then obtain electrons easily. 相似文献
A facile strategy for preparing vertically aligned polypyrrole (PPy) nanoarrays with precisely controlled density and quantity is presented. The method involves two steps: (1) the fabrication of the patterned substrate via electron beam lithography and (2) the controlled growth of PPy nanowires via electrochemical polymerization on the patterned substrate. The electrical property of a single PPy nanowire is investigated via in situ conducting probe atomic force microscopy. 相似文献