Guaiacol-substituted silanes as selectivity control agents for Ziegler-Natta polypropylene catalysts

Several series of silanes containing at Least one guaiacol moiety were conv eniently prepared by direct treatment of dichlorosilanes with o-methoxyphen ol (guaiacol) in the presence of triethylamine. After isolation and charact erization, the compounds were evaluated as external donors (or selectivity control agents, SCAs), for heterogeneous fourth-generation Ziegler-Natta ca talysts in liquid propylene (LIPP) polymerizations. The isotactic polypropy lene polymers formed using these SCAs covered a wide range of xylene solubl es from similar to5% to 16%. The most effective guaiacol-containing SCAs we re those containing both sterically bulky groups on the central silicon ato m as well as an attached methoxy group.