ANALYSIS OF THE MICROPOROSITY OF NASCENT POLYETHYLENE - XE-129 NMR AND HIGH-RESOLUTION ADSORPTION

During the initial stages of ethylene polymerization, the product polymer forms on the surface and eventually fills the void space of the catalyst. In later stages of polymerization, the catalyst fragments and the surface accessible to the gas phase decreases precipitously. These studies focus on the initial polymer formed on the surface to determine if its morphology is different than the polymer formed at higher yield. Several earlier studies had suggested that the structure of the polymer formed on the catalyst during the initial stages of polymerization is different from the rest of the bulk polymer structure. High resolution adsorption (HRADS) and Xe-129 NMR experiments were used to confirm the existence of a organic microporous structure formed by the polymer and sorbed on the catalyst surface. Both independent techniques, HRADS and Xe-129 NMR, performed on low yield catalyst/polymer samples, detected some microporosity that disappeared at higher polymer yield or higher polymer loading of the catalyst.