Preparation of Polycinnamamide Catalyzed by Palladium-Graphite through the Heck Reaction

Palladium-graphite (Pd-Gr) was successfully used as a heterogeneous catalyst for the preparation of polycinnamamide through the Heck reaction. The condensation reaction of ethyl acrylate and iodobenzene catalyzed by Pd-Gr proceeded efficiently in the presence of tributylamine in an aprotic polar solvent such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO). The polymerization of N,N'-(3,4'-oxydiphenylene)bis-(acrylamide) and bis(4-iodophenyl) ether catalyzed by Pd-Gr was carried out in the presence of tributylamine in DMF at 100 °C. The polymerization proceeded efficiently to form polycinnamamide, but required a longer reaction time compared to the polycondensation catalyzed by palladium acetate. The structure of the resulting polymer was confirmed as trans-polycinnamamide by two-dimensional NMR measurements. The resulting polymer was almost white, which means that it was less contaminated by palladium metal. The removal and recycling of Pd-Gr were much easier than in the case of homogeneous catalysts.