Biomedical subjects

Dave J Adams

Publications and source records attributed to Dave J Adams.

6 recordsLinked to original sources

PubMed2006

Janus particles at liquid-liquid interfaces.

Following recent theoretical predictions, we report on the first experiments on the interfacial activity of so-called Janus nanoparticles (i.e., bifacial particles consisting of a gold and an iron oxide moiety). Using pendant drop tensiometry, we show that the amphiphilicity derived from the Janus character of the particles leads to a significantly higher interfacial activity compared to that of the respective homogeneous particles of the same size. The self-assembly of Janus particles at the hexane-water interface results in a significant decrease in the interfacial tension. Furthermore, we demonstrate control over the interfacial activity by tuning the particles' amphiphilicity via ligand-exchange reactions.

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PubMed2006

Effect of block length, polydispersity, and salt concentration on PEO-PDEAMA block copolymer structures in dilute solution.

A series of poly(ethylene oxide)-block-poly(N,N-diethylaminoethyl methacrylate) (PEO-PDEAMA) block copolymers with relatively high polydispersity (1.36 < PDI < 1.96) have been prepared to determine the effect that polydispersity has on the self-assembly of amphiphilic block copolymers in dilute solution. Because monodisperse macroinitiators were used for the ATRP reactions, the polydispersity resides within the hydrophobic block. By adjusting the relative block lengths, spherical micelles, wormlike micelles, vesicles, or a precipitate is formed. Here, we show that relatively high polydispersity in the block copolymer does not preclude efficient self-assembly. We also discuss the effect of increasing the concentration of NaCl in the systems and show that this can result in a shift from one morphology to another. These shifts are reversible in some cases, but for PEO12-PDEAMA39, this method allows access to giant vesicles of between 500 nm and 1 microm in diameter.

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PubMed2005

Rhodium catalysed hydroformylation of alkenes using highly fluorophilic phosphines.

Highly fluorophilic phosphines incorporating at least one aromatic ring containing two directly attached perfluoroalkyl groups have been synthesised, their partition coefficients (organic phase : fluorous phase) measured and their electronic properties probed using (1)J(PtP) data for their trans-[PtCl(2)L(2)] complexes. These phosphines have been used as modifying ligands for the rhodium catalysed hydroformylation of 1-octene in perfluorocarbon solvents. Catalyst activity, regioselectivity and the levels of rhodium leaching to the product phase vary with the substitution patterns of the modifying ligands that do not correlate with the electronic properties or partition coefficients of these ligands, but can be interpreted in terms of differences in the resting states of the catalysts.

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PubMed2004

Manipulation of the stereochemical outcome and product distribution in the Henry reaction using CO2 pressure.

The rate and stereocontrol of the Henry reaction in the presence of CO(2) can be controlled simply by manipulation of CO(2) pressure, and can be understood by consideration of the kinetic and thermodynamic aspects of the reaction.

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PubMed2004

The design of a continuous reactor for fluorous biphasic reactions under pressure and its use in alkene hydroformylation.

A reactor, into which all reagents can be fed continuously and from which the reaction mixture can be continuously removed to a gravity separator, where product can be continuously removed and the catalyst phase recycled to the reactor, has been constructed and used for the hydroformylation of alkenes in fluorocarbon solvents.

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PubMed2002

Hydroformylation in fluorous solvents.

Triaryl-phosphines and -phosphites bearing fluorous ponytails give high rates, good linear selectivity and good retention of catalyst in the fluorous phase during hydroformylation of alkenes in fluorous solvents.

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