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The S,Ar substitutions of a number of 5-X-substituted indoles (1 a-f ), 5-X-substituted 2methylindoles (1 g-j) and N-methylindole (1 k) by 4,6-dinitrobenzofuroxan (DNBF) have been kinetically studied in 70-30 (v/v) H,O-Me,SO, 50-50 (v/v) H,O-Me2S0, methanol and acetonitrile. The absence of a significant dependence of the rates of reactions on the hydrogen or deuterium labelling at C-3 of the indole ring indicates that electrophilic attack (kyNBF) by DNBF at this position is the rate-limiting step of the substitutions. However, the kYNBf rate constants are strongly sensitive to the solvent polarity, the observed reactivity sequence being 70-30 H,O-Me,SO > 50-50 H,O-Me,SO > methanol > acetonitrile. This trend is consistent with a highly 10 7

The syntheses of several functionalised aryl cyanate esters bearing reactive allyl groups are presented. The monomers were purified (to c. 98%) using preparative HPLC and a range of techniques, including heteronuclear nuclear magnetic resonance (NMR) spectroscopy, was employed in their characterisation. A model functionalised aryl cyanate ester was doped with a variety of additives and the resulting thermal behaviour examined using dynamic differential scanning calorimetry (DSC). Furthermore, the postulated co‐reaction of the model functionalised cyanate ester with bis‐maleimides was investigated using heteronuclear NMR and dynamic mechanical techniques.

A series of copper complexes of epoxy-imidazole adducts have been prepared and characterized by 'H nuclear magnetic resonance (NMR) spectroscopy. Differential scanning calorimetry (DSC) was employed to investigate the thermal behaviour of the curing agents and to investigate the medium-term storage stability of a one-pot composition of a commercial epoxy resin when mixed with the complexes. The cure onset temperatures of the mixtures containing copper complexes are ca. 2 0 4 0°C higher than those of the parent epoxy-imidazole adducts and the decrease of cure onset temperatures in the early stages of storage (up to 100 h) is less. The latent nature and improved storage stability of mixtures containing the copper complex were clearly demonstrated and confirmed by the viscosity bahaviour of the catalysed mixtures of the commercial epoxy resins MY720 and MY750. 'H NMR and electron paramagnetic resonance (EPR) spectroscopy were employed to monitor the thermal decomposition of the copper(i1) complexes, which were found to decompose at 120-1 30 "C and exist in equilibrium. Glass fibre-reinforced composite samples were prepared using a commercial epoxy resin cured with the complexes and their physico-mechanical properties were evaluated.Owing to their extreme versatility, epoxy resins are used extensively in industrial applications in which they are required to cure quickly and be readily formulated as onepot compositions (i.e. the epoxide and catalyst are stored as a mixture rather than as two separate materials that have to be mixed prior to use). This in turn means that the composition must have a stability of at least several months at ambient temperature. Imidazoles are used as epoxy curing agents owing to their fast catalytic action and also the fine mechanical properties which they produce in the cured resin. Some imidazoles are highly effective epoxy curing agents,' and recent have demonstrated that epoxy resins cured with imidazoles can have superior physical properties (e.g. better heat resistance, lower tensile elongation, a higher modulus and a wider range of cure temperatures) than amine-cured resulting in their wide usage in the electronics industry as moulding and sealing compounds. Imidazoles are added to epoxy systems to catalyse the homopolymerization of epoxide groups (polyetherification), but unmodified imidazoles have low stability when mixed with epoxies (curing occurs slowly at room temperature) making them unsuitable for use in one-pot compositions.Much work has been carried out on stabilizing imidazoles for use as latent epoxy curing agents and one approach involves the preparation of metal-imidazole complexes.435 Transition metals have been used to prepare such complexes and these have exhibited good stability at room temperature and a rapid cure at elevated temperatures. Most metal-imidazole complexes are crystalline materials with very low solubility in common epoxides.6 Solubility of the curing agent in the epoxide is very desirable because heterogenous dispersions are liable to settle out or...

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