Solution behavior of poly(styrene)-block-poly(2-vinylpyridine micelles containing gold nanoparticles

Formation and structural transformation of inverse poly(styrene)-block-poly(2-vinylpyridine) micelles whose polyvinylpyridine core was loaded with HAuCl4 or with elementary gold nanoclusters was studied by combined static and dynamic light scattering. A transformation in the morphology from spherical particles (small Rg/Rh ratio) to large anisomeric objects (large Rg/Rh ratio) was observed by decreasing the concentration of the block copolymer below the critical micelle concentration. At this point, the polymer chains are molecularly dispersed and no longer able to prevent uncontrolled growth of the gold nanoclusters

Controlled mineralization and assembly of hydrolysis-based nanoparticles in organic solvents combining polymer micelles and microwave techniques

Controlled formation of nanoparticles in inverse diblock copolymer micelles by hydrolysis of titanium alkoxide precursors is described. Coagulation of the resulting TiO2-loaded micelles occurs on casting if the sample is prepared by conventional heating, allowing strings of TiO2 particles to form (see Figure). It is demonstrated that this can be prevented by microwave heating

Generation of Annelated Dicarbenes and Their Alkali-Metal Chelate Complexes in Solution : Equilibrium between Hetero- and Homoleptic NHC Lithium Complexes

Attempts to generate the free bis­(N-heterocyclic carbene) vegi^R (R = <i>n</i>Pr, <i>t</i>Bu; vegi^R = 2,7-dihydro-2,7-dialkyldiimidazo­[1,5-<i>b</i>:5′,1′-<i>f</i>]­pyridazine-1,8-diylidene) from its imidazolium salts <b>1</b> with alkali-metal bases resulted exclusively in the formation of the respective lithium, sodium, and potassium complexes <b>2</b>–<b>4</b> due to the strongly chelating properties of the dicarbene. DFT calculations reveal pronounced dispersion interactions in the case of <i>N-tert</i>-butyl substituents as the reason for the formation of the homoleptic lithium species <b>2b-H</b> in solution. The dynamic behavior of the lithium complexes in equilibrium was studied by NMR techniques. Attempts to liberate the free carbenes by addition of the respective crown ethers failed for the lithium and sodium complexes. Deprotonation of the imidazolium salts <b>1a</b>,<b>b</b> with the strong metal-free phosphazene base P4-<i>t</i>Bu ({(Me₂N)₃PN}₃PN<i>t</i>Bu) generated successfully the free dicarbenes vegi^R (<b>5</b>) and monocarbene <b>6b</b> in solution