Calixarenes as a new class of external electron donors in Ziegler-Natta polypropylene catalysts

In this work we have shown that calixarenes form a new type of external don or ligand which can function effectively as a selectivity control agent to increase the yield of isotactic polypropylene in late-generation Ziegler-Na tta catalysts. The procatalyst prepared utilized dibutylphthalate as the in ternal donor to function with the calixarene. We have synthesized and chara cterized a wide variety of new substituted calixarenes containing hydroxy- and methoxy-end groups. All of these calixarenes were evaluated in the bulk polymerization of propylene and found to increase significantly the amount of i-PP formed relative to reactor runs performed without the calixarene. (C) 1999 Elsevier Science B.V. All rights reserved.