Manipulating interfacial polymer structures through mixed surfactant adsorption and complexation

The effects of a nonionic alcohol ethoxylate surfactant, C(13)E(7), on the interactions between PVP and SDS both in the bulk and at the silica nanoparticle interface are studied by photon correlation spectroscopy, solvent relaxation NMR, SANS, and optical reflectometry. Our results confirmed that, in the absence of SDS, C(13)E(7) and PVP are noninteracting, while SDS interacts strongly both with PVP and C(13)E(7) . Studying interfacial interactions showed that the interfacial interactions of PVP with silica can be manipulated by varying the amounts of SDS and C(13)E(7) present. Upon SDS addition, the adsorbed layer thickness of PVP on silica increases due to Coulombic repulsion between micelles in the polymer layer. When C(13)E(7) is progressively added to the system, it forms mixed micelles with the complexed SDS, reducing the total charge per micelle and thus reducing the repulsion between micelle and the silica surface that would otherwise cause the PVP to desorb. This causes the amount of adsorbed polymer to increase with C(13)E(7) addition for the systems containing SDS, demonstrating that addition of C(13)E(7) hinders the SDS-mediated desorption of an adsorbed PVP layer.     

In situ synthesis of Cu-BTC (HKUST-1) in macro-/mesoporous silica monoliths for continuous flow catalysis

The metal-organic framework Cu-BTC has been successfully synthesized as nanoparticles inside the mesopores of silica monoliths featuring a homogeneous macropore network enabling the use of Cu-BTC for continuous flow applications in liquid phase with low pressure drop. High productivity was reached with this catalyst for the Friedl?nder reaction.     

Engineered 3D microporous gelatin scaffolds to study cell migration

Here we present a facile method to fabricate microporous hydrogel scaffolds that can be functionalized with a chemokine gradient. These scaffolds allow studying cellular responses in a 3D environment.     

Synthesis of poly(4-vinyl pyridine-b-methyl methacrylate) by MAMA-SG1 initiated sequential polymerization and formation of metal loaded block copolymer inverse micelles

Well-defined poly(4-vinylpyridine) (P4VP) was synthesised by nitroxide-mediated radical polymerization using the BlocBuilder MAMA-SG1. The controlled character of the polymerization was confirmed by kinetic measurements and linear increase of the molar mass with monomer conversion. Poly(4-vinylpyridine) terminated with SG1 was then used as macroinitiator and chain extended to form poly(4-vinylpyridine-b-methyl methacrylate) and poly(4-vinylpyridine-b-(methyl methacrylate-co-styrene)) block copolymers. These block copolymers spontaneously organized into spherical inverse micelles in THF with critical micelle concentrations of 0.1 mg/mL for poly(4VP₁₉₀-b-MMA₉₁) and 0.01 mg/mL for poly(4VP₁₉₀-b-(MMA₅₇-co-S₁₈)) and sizes of 70 and 130 nm (DLS), respectively. The inverse micelles were loaded with copper(II)acetate leading to a slight increase in micelle size. The uniform structure of the inverse micelles was confirmed by FeSEM images, while the presence of copper in the micelle core was established by energy-dispersive X-ray spectroscopy (EDX) and FTIR spectroscopy.     

Energy transfer pathways in dinuclear heteroleptic polypyridyl complexes: through-space vs through-bond interaction mechanisms

A series of homo- and heteronuclear ruthenium and osmium polypyridyl complexes with the bridging ligands 1,3-bis(5-(2-pyridyl)-1H-1,2,4-triazol-3-yl)benzene (H(2)mL) and 1,4-bis(5-(2-pyridyl)-1H-1,2,4-triazol-3-yl)benzene (H(2)pL) are reported. The photophysical properties of these compounds are investigated, and particular attention is paid to the heteronuclear (RuOs) compounds, which exhibit dual emission. This is in contrast to phenyl-bridged polypyridine Ru-Os complexes with a similar metal-metal distance, in which the Ru emission is strongly quenched because the nature of the bridging ligand allows for an efficient through-bond coupling. The results obtained for the compounds reported here suggest that energy transfer is predominantly taking place via a dipole-dipole, F?rster type, mechanism, that may dominate when through-bond coupling is weak. This is in stark contrast to ground state interaction, which is found to be critically dependent on the nature of the bridging unit employed.     

Aromatic lead(IV) compounds : VIII. 13C FT-NMR spectroscopy of compounds Arn Pb(CH3)4−n (n = 0–4)

¹³C chemical shifts and ²⁰⁷Pb¹³C coupling constants are reported for some arylmethyllead compounds. The value of J(²⁰⁷Pb¹³C) is shown to depend on the number and the nature of the aryl groups.