Six polymer-supported Mo"' catalysts have been prepared. T w o involve supported aminomethyl-2pyridine (AMP) ligands, and the other four various ligands based o n imidazole. All catalysts are active in the epoxidation of propene using tert-butyl hydroperoxide in the liquid state at 80 "C and at a pressure of 400 psi (He). The catalysts w i t h AMP ligands show a slight fall in activity on recycling, but this trend is also accompanied by significant and continuing leaching of Mo. In contrast the catalysts based o n imidazole-containing polymers generally show better retention of catalyst activity, and most importantly n o measurable loss of M o after the first few cycles. The best species is based on polybenzimidazole, PBI. This shows only modest activity when used initially but when the catalyst is recycled the conversion in the reaction rises to 99.8% and the selectivity is essentially 100%. Thermogravimetric analysis also shows that this polymer-supported catalyst is stable in air to ca. 400 "C, and so also offers the possibility of application under even more extreme oxidative conditions than those used t o date.

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Polyimide oligomers (prepolymers) and resins of the PMR-15 type have been prepared from 5-norbomene-2,3-dicarboxylic half acid ester (NE), 3,3',4,4'-benzophenone tetracarboxylic diester (BTDE) and a series of diamines incorporating 1,2,3-triazole, quinoxaline, pyrido[2,3-b]pyrazine, pyrido[3,4-b]pyrazine, benzo[g]quinoxaline, pyrazino-[2,3]-d]pyridazine and bis(pyrido[3,4-b]pyrazino)benzene ring systems. Two tetraamines in the bis(pyrazino[2,3-d]pyridazino)benzene ring system were also employed. Selected diamine monomers from the above ring systems provde PMR-15-analogue resins of higher thermal and thermooxidative stability than PMR-15 itself. The physical behaviour during oligomerization and curing of PMR systems has been studied by dynamic mechanical thermal analysis (DMTA). Traces akin to that from PMR-15 are obtained using certain diamine monomers (e.g. triazole and pyrido[3,4-b]pyrazine containing) but a featureless thermogram is observed using tetraamines in the bis(pyrazino[2,3-dj]pyridazino) benzene system.

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