Synthesis and [2+2]-photodimerisation of monothiomaleimide functionalised linear and brush-like polymers

[2+2]-Photodimerisation of monothiomaleimides has been demonstrated on functionalised linear and brush-like polymers. In water/acetonitrile (95 : 5) mixtures the rate of reaction is accelerated significantly by irradiation of the thiomaleimide end group (λmax = 350 nm) with UV light, reaching full conversion within 10 minutes

Unprecedented solvent-induced acceleration of free-radical propagation of methyl methacrylate in ionic liquids.

The rate of propagation in the free-radical polymerization of methyl methacrylate in an ionic liquid has been determined and shows unprecedented solvent-induced acceleration, partially explaining the surprising increase in overall rates of polymerization and molecular weights in these solvents

Pulsed laser polymerization in an ionic liquid: Strong solvent effects on propagation and termination of methyl methacrylate

The rate constants of propagation and termination of methyl methacrylate (MMA) in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate were measured using the pulsed laser polymerization technique across a range of temperatures, and Arrhenius parameters were calculated for the rate of propagation at ionic liquid concentrations of 0, 20, and 50% v/v. Point estimates for these values are A = 2.4 × 10 6 L mol -1 s -1 (0% v/v ionic liquid), 2.1 × 10 6 L mol -1 s -1 (20% v/v), and 2.5 × 10 6 L mol -1 s -1 (50% v/v) and E A = 22.1 kJ mol -1 (0% v/v), 21.0 kJ mol -1 (20% v/v), and 20.4 kJ mol -1 (50% v/v). The decrease in activation energy leads to large increases in the rate of propagation. In addition, the rate of termination decreases by an order of magnitude as the ionic liquid concentration is increased to 60% v/v. The increase in propagation rate was attributed to the increased polarity of the medium, while the decrease in the termination rate is due to its increased viscosity

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. (C) 2002 Elsevier Science Ltd. All rights reserved

COBALT-MEDIATED FREE-RADICAL POLYMERIZATION OF ACRYLIC-MONOMERS

The use of square-planar low-spin cobalt complexes to control the free-radical polymerization of vinyl monomers is described. The control exerted depends on both the catalyst and the monomer structure. Monomers with a beta-hydrogen (for example, methacrylates) undergo catalytic chain transfer, which is a powerful synthetic technique for producing macromonomers. Monomers without a beta-hydrogen (for example, acrylates) are capable of pseudo-living polymerization by exploitation of the 'persistent radical' effect. The structure of the cobalt complex is shown to be very important in determining its catalytic activity