One-step synthesis of hyperbranched dendritic polyesters

The one-step synthesis of a hyperbranched polyester possessing a dendritic structure has been achieved by thermal self-condensation of 3,5-bis(trimethylsiloxy)benzoyl chloride. The hyperbranched polyesters are obtained in yields of 80% or greater and with polystyrene equivalent weight average molecular weights in the range 30000 to almost 200000. The polydispersity and the molecular weights of the polyesters were found to vary greatly with the temperature of the polymerization. Characterization of the polymers was readily accomplished by NMR spectroscopy with the help of model compounds. The degree of branching of the polyesters as determined from NMR experiments was between 55 and 60%. The polyesters, which contain reactive functional groups at all chain extremities, are glassy materials that show a very high thermal stability comparable to that of analogous linear materials. In contrast, the excellent solubility properties of the hyperbranched polyesters influenced by their shape and functionalization are at variance with those of their linear polyester analogues.