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Poly(N-cyanoethylethyleneimine) (PCEI) obtained by Michael addition of linear poly(ethyleneimine) (LPEI) with acrylonitrile provided novel nanocrystalline entities which could serve as catalytic templates affording nanosheet-based structured silica under mild conditions. [ABSTRACT FROM AUTHOR]

The formation of hierarchical aggregates from linear polyethyleneimine (LPEI) was performed in aqueous media containing a series of divalent metal ions (MnII, FeII, CoII, NiII, CuII, ZnII) and their organization processes are investigated by transcribing the structure into hard silica frames which can be appropriately characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF) measurements. Coexisting metal salts interact with LPEI viacoordination bonds between metal ions and amine groups in ethyleneimine (EI) units to form water-soluble complexes. Without suitable complexation, LPEI crystallizes without restriction and forms non-well controlled hierarchical microstructures even in the presence of metal ions. The molar ratios of EI units and metal ions strongly affect the morphologies of crystalline precipitates. Low values of the ratios lead to intricate flower-like structures composed of leaf-like fibers assembled in a random fashion. On the other hand, an increase of the ratios makes the structures well-shaped and flattened for constructing 2-D turbine-like morphology. These structures consist of numerous sheet structures grown in a radial fashion. XRD and XRF measurements reveal that these resulting solids are mainly composed of hydrated LPEI and imply that coordinating metal ions are located in the peripherals of LPEI microstructures. Finally, temporal morphological evolution experiments indicate that a metal ion which can coordinate with EI units serves as a regulator in the crystallization of LPEI and abundant crystal growth can proceed. [ABSTRACT FROM AUTHOR]

Silica deposition by mediation of aggregated linear poly(ethyleneimine) (LPEI) from a basic aqueous solution of sodium silicate can produce ordered silica with fibrous bundle structure hybridized with LPEI via zero-emission of organic by-products. By changing the polymer concentration and pH value of the aqueous solution of sodium silicate, we were able to control the architecture of the resulting silica. This process is environmentally benign and inexpensive and thus would be feasible for industrial scale-up for the fabrication of silica nanomaterials. In addition, a typical fibrous silica bundle was characterized by fluorescence X-ray analysis, solid state 29Si (CP/MAS) NMR, TG/DTA, thermo-calcination, N2/He adsorption–desorption experiments, and high resolution TEM. Interestingly, the fibrous silica bundle, which contains about 25% LPEI, served as an effective nanoreactor to reduce metal ions into nearly cluster-size metallic nanoparticles inside the silica. [ABSTRACT FROM AUTHOR]

Ionic iron complex [(Me3tacn)2Fe2Cl3]+[(Me3tacn)FeCl3]−(1), which is readily soluble in methanol, acted as a powerful catalyst in controlled radical polymerization of styrene and MMA, and showed promising features of removal from the resulting polymers and was reusable after recovery from the crude products. [ABSTRACT FROM AUTHOR]