Carl Waterson

Improved Reproducibility and Increased Signal Intensity in Matrix-assisted Laser Desorption/Ionization as a Result of Electrospray Sample Preparation†

Electrospray preparation of sample slides for matrix-assisted laser desorption/ionization has proved to minimize both sample spot-to-spot and shot-to-shot variations compared to traditional deposition by spotting.

Copper(0)-Mediated Living Radical Polymerization of Methyl Methacrylate in a Non-polar Solvent.

The metal catalyzed polymerization of methyl methacrylate using Cu(0) as the catalyst source has been investigated in toluene. This work looks at polymerizations in a non-polar medium allowing control over the molecular weight and polydispersity with a 4-fold reduction in catalyst concentration versus conventional ATRP, while the use of an active ligand allows the reaction to proceed at room temperature. The use of an excess of PMDETA ligand allows for high conversions, and the addition of a small amount of CuBr(2) enhances living characteristics, enabling efficient chain extension.

Determination of end groups of synthetic polymers by matrix-assisted laser desorption/ionization: high-energy collision-induced dissociation.

Matrix-assisted laser desorption/ionization has been combined with high-energy collision-induced dissociation for the analysis of poly(ethylene glycols) with butanoyl, benzoyl and acetyl end groups, using novel technology comprising a magnetic-sector mass spectrometer and ion buncher with an in-line quadratic-field ion mirror. High-energy (>8 keV) collision-induced dissociation facilitated unambiguous end-group determination of these polymers, providing masses of end groups and structural information. The high-energy collision-induced dissociation also provided information regarding repeat units.

Monohydroxy terminally functionalised poly(methyl methacrylate)from atom transfer radical polymerisation

Atom transfer radical polymerisation (ATRP) of methyl methacrylate with a pyridinecarbaldehyde imine copper(I) catalyst and hydroxy functional alkyl bromide initiator leads to α-hydroxy functional PMMA with controlled M n and PDI < 1.20 without the use of protecting group chemistry.

Novel polymers from atom transfer polymerisation mediated by copper(I) Schiff base complexes

The use of copper(I) Schiff base complex catalysed atom transfer polymerisation of methacrylates is described. The use of a range of functional and multi-functional initiators enables the synthesis of a range of functional and star polymers to be prepared under undemanding synthetic conditions. End capping with silyl enol ethers allows for ω-functional polymers. The combination of novel initiators, functional monomers and end capping allows an unprecedented array of macromolecular structures to be produced with limited need for protecting group chemistry.

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.

Comment: A simple, low-cost, air-spray method for improved sample preparation for matrix-assisted laser desorption/ionisation mass spectrometry of derivatised poly(ethylene glycol)

A simple, low-cost, air-spray technique has been evaluated for the preparation of matrix-assisted laser desorption/ionisation (MALDI) sample slides. Hydroxyl end groups of poly(ethylene glycol) Mn = 600 were functionalised by esterification using acetyl and butyryl chlorides. Air-spray deposition gave excellent shot-to-shot and spot-to-spot reproducibility; the observed compositions by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) being in agreement with those obtained from 1H NMR. Compressed air-spray is an excellent, inexpensive, sample preparation procedure for simple routine MALDI-TOF MS which increases the reproducibility of this increasingly important technique for synthetic polymer analysis.

Polyolefin-polar block copolymers from versatile new macromonomers

A new metallocene-based polymerization mechanism is elucidated in which a zirconium hydride center inserts α-methylstyrene at the start of a polymer chain. The hydride is then regenerated by hydrogenation to release a polyolefin containing a single terminal α-methylstyrenyl group. Through the use of the difunctional monomer 1,3-diisopropenylbenzene, this catalytic hydride insertion polymerization is applied to the production of linear polyethylene and ethylene-hexene copolymers containing an isopropenylbenzene end group. Conducting simple radical polymerizations in the presence of this new type of macromonomer leads to diblock copolymers containing a polyolefin attached to an acrylate, methacrylate, vinyl ester, or styrenic segments. The new materials are readily available and exhibit interfacial phenomena, including the mediation of the mixing of immiscible polymer blends.