Adrian J. Carmichael

First report of reversible addition-fragmentation chain transfer (RAFT) polymerisation in room temperature ionic liquids.

The Reversible Addition-Fragmentation chain Transfer (RAFT) polymerisation of acrylates, methacrylates and styrene is reported for the first time in room temperature ionic liquids; the acrylate and methacrylate polymerisations show a living character and lead to well-characterised polymers, with narrow polydispersity (< 1.3); in the case of styrene, the insolubility of the polymer in the ionic liquids stops the polymerisation at an early stage.

Molecular layering and local order in thin films of 1-alkyl-3-methylimidazolium ionic liquids using X-ray reflectivity

X-ray reflectivity measurements in air of thin films of 1-alkyl-3-methylimidazolium salts in the liquid, liquid crystalline and solid states supported on Si(111) are described. The films show Bragg features in both liquid crystalline and solid phases, but only after an initial annealing cycle. Kiessig fringes are observed only for the 1-octadecyl-3-methyl-imidazolium hexafluorophosphate films and, following analysis using Parratt32, a bi-layer model is proposed whereby the molecules are orientated with ionic groups at both salt-air and salt-silicon interfaces.

In Vitro and ex Vivo Intestinal Tissue Models to Measure Mucoadhesion of Poly (Methacrylate) and N-Trimethylated Chitosan Polymers

No HeadingPurpose.The adhesion of a range of polymers based on poly(2-(dimethylamino-ethyl) methacrylate (pDMAEMA) was assessed using human mucus-secreting and non mucus-secreting intestinal cell monolayers, HT29-MTX-E12 (E12) and HT29 monolayers, as well as excised non-everted intestinal sacs from rats. Differentiation of mucoadhesion from bioadhesion was achieved by pre-treatment with the mucolytic agent, N-acetyl cysteine (NAC). Adherence of pDMAEMA polymers was compared to that obtained with the mucoadhesive, N-trimethylated chitosan (TMC).Methods.The quantity of adherent coumarin 343-conjugated polymers to HT29, E12, and intestinal sacs was measured by fluorescence. Confocal laser scanning microscopy (CLSM), light microscopy, and fluorescent microscopy were used to provide direct evidence. Measurements of transepithelial electrical resistance (TEER), permeability to FITC-dextran 4000 (FD-4), and the release of lactate dehydrogenase (LDH) were used to assess potential cytotoxicity of polymers.Results.Adherence of unquaternized and of 10%, 24%, and 32% methyl iodide-quaternized pDMAEMA polymers was measured in E12, HT29, and sacs. All pDMAEMA polymers showed significantly higher levels of adhesion to mucus (mucoadhesion) than to epithelium (bioadhesion). Colocalization of pDMAEMA with mucus was confirmed in E12 by microscopy. TMC showed equally high levels of mucoadhesion as unquaternized and 24% quaternized pDMAEMA, but displayed higher levels of bioadhesion. pDMAEMA-based polymers demonstrated lower levels of adherence to E12 and rat sacs in the presence of NAC, whereas adherence of TMC was unchanged. pDMAEMA significantly decreased the permeability of FD-4 across E12 monolayers and sacs and was less cytotoxic in E12 than in HT29. In contrast, TMC increased the permeability of FD-4 across E12 and sacs and was less cytotoxic in E12 than in HT29.Conclusions.Human mucus–producing E12 monolayers can be used to assess polymer mucoadhesion and give similar data to isolated rat intestinal sacs. pDMAEMA displayed similar levels of mucoadhesion and lower levels of bioadhesion than a chitosan derivative and it was not cytotoxic. pDMAEMA decreased FD-4 flux in the presence of mucus, whereas TMC increased it. The combination of mucus and methacrylate polymers appears to increase barrier function of the apical membrane.

Reversible addition–fragmentation chain transfer polymerization of methacrylate, acrylate and styrene monomers in 1-alkyl-3-methylimidazolium hexfluorophosphate

1-alkyl-3-methylimidazolium hexfluorophosphate ([C-x][PF6], where x = 4, 6-8) is used as solvent for the polymerisation of methyl methacrylate, methyl acrylate and styrene by the reversible addition-fragmentation chain transfer process. In the case of styrene, the insolubility of the polymer in ionic liquid stops the polymerization at an early stage. The acrylate and methacrylate polymerizations lead to products with molecular weights close to the theoretical ones and polydispersity indexes lower than 1.3. The polymerizations are shown to be living by chain extension of the products formed in ionic liquid. In the case of the methyl methacrylate, the kinetics of the polymerizations are followed and the molecular weight of the polymer is shown to increase linearly with the conversion, as expected for a living polymerization

Synthesis of functional polymers by living radical polymerisationBasis of a presentation given at Materials Discussion No. 6, 12?14th September 2003, Durham, UK.Electronic supplementary information (ESI) available: synthesis and characterization of initiators 2, 3 and 5?7. See http://www.rsc.org/suppdata/jm/b3/b303759b/

The use of copper(I) halides in conjunction with pyridine imine ligands is reported to lead to a range of controlled molecular weight and architecture polymers. The use of multifunctional initiators leads to di-, tri- and tetra-functional star polymers based on pentaerythritol cores. The polymerisations all follow excellent first order kinetics with Mn increasing linearly with conversion. The polymerisation is first order in copper halide. A range of α-functional polymers with 4-[(4-chloro-6-methoxy-1,3,5-triazin-2-yl)amino]phenyl 2-bromo-2-methylpropionate, N-hydroxysuccinimide and phthalimide have been prepared which introduce terminal functionality into polymers for subsequent coupling and potential synthesis of conjugates for biologically active compounds. Finally block/graft amphiphilic copolymers are demonstrated via the preparation of a statistical copolymer macroinitiator containing a hydroxy functionality which is used for the polymerisation of dimethylaminoethyl methacrylate prior to esterification of the hydroxy functionality to give living radical polymerisation initiators which are used subsequently in the polymerisation of methyl methacrylate. Copper(I) mediated living radical polymerisation is shown to be an effective method for the synthesis of a range of functional synthetic polymers.

Synthesis and characterisation of cationic bis(cyclopentadienyl)tungsten(IV) complexes

Cationic hydride complexes of bis(cyclopentadienyl)tungsten(IV) have been prepared and studied. The complex [W(η-C5H5)2H(thf)][SO3CF3] reacts with CS2 in d6-acetone to form the chelated O-alkyl dithiocarbonate tungsten hydride insertion product [W(η-C5H5)2(η2-S2COCH(CD3)2-S,S′)][SO3CF3] as demonstrated by single crystal X-ray diffraction and NMR spectroscopy. The styrene complex [W(η-C5H5)2H(η2-CH2CHC6H5)][PF6] has been prepared as a mixture of exo and endo isomers. This isomeric mixture reacts thermally with NCMe to give [W(η-C5H5)2(CH2CH2C6H5)(NCMe)][PF6] and photochemically with NCMe to give [W(η-C5H5)2H(NCMe)][PF6]. The molecular structures of the exo isomer and of the benzonitrile complex [W(η-C5H5)2H(NCPh)][SO3CF3] are reported.

Synthesis of[W(η5-C5H5)2H(L)] and[W(η5-C5H5)2L2]2+ cations (L = NCMe, NCPh,C4H8O or CNBut). Crystal and molecularstructures of[W(η5-C5H5)2H(C4H8O)][CF3SO3] and[W(η5-C5H5)2(NCMe)2][CF3SO3]2

The cationic hydride complexes [W(η-C 5 H 5 ) 2 H(L)][CF 3 SO 3 ] [L = NCMe, NCPh, tetrahydrofuran (thf) or CNBu t ] have been synthesized by reaction of [W(η-C 5 H 5 ) 2 H 2 ] and methyl trifluoromethanesulfonate in the presence of the σ-donor ligand L. Kinetic measurements on ligand-substitution reactions in CD 3 CN solution indicate that L is labile in solution; [W(η-C 5 H 5 ) 2 H(L)] + cations have half-lives of 315(10), 122(6) and 6.68(5) h (L = NCMe, NCPh or thf respectively) at 44 °C. The activation energy E a for tetrahydrofuran substitution in [W(η-C 5 H 5 ) 2 H(thf)] + is 132 ± 1 kJ mol -1 . An X-ray crystallographic determination of the structure of [W(η-C 5 H 5 ) 2 H(thf)][CF 3 SO 3 ] demonstrates that the tetrahydrofuran ligand is oriented ‘in-plane’ with the centroid–W–centroid plane, indicating that the thf acts as a simple σ-donor ligand. Reaction of [W(η-C 5 H 5 ) 2 H 2 ] with an excess of CF 3 SO 3 Me yields the dicationic tungstenocene complex [W(η-C 5 H 5 ) 2 (NCMe) 2 ][CF 3 SO 3 ] 2 as demonstrated by IR and NMR spectroscopy and X-ray crystallography.

Synthesis and characterisation of cationic bis(cyclopentadienyl)tungsten(IV) complexes containing alkyl, chloride and hydride ligands

The cationic complexes [W(η-C5H5)2R(NCMe)][PF6](R = Et or H), [W(η-C5H5)2Me(NCR′)][BF4] and [W(η-C5H5)2Cl(NCR′)][BF4](R′= Me or Ph) have been prepared and characterised by 1H and 13C NMR and IR spectroscopy, and by X-ray crystallography in the case of [W(η-C5H5)2Et(NCMe)][PF6]. The complex [W(η-C5H5)2H(NCMe)][PF6] is unstable in solution at room temperature, decomposing slowly to yield the dinuclear C–H activation product [{W(η-C5H5)(µ-η1:η5-C5H4)(NCMe)}2][PF6]2 as demonstrated by NMR spectroscopy and X-ray crystallography.