Abstract
The catalyst VOCI 3 ( C 2 H 5) 2 AICI was used to prepare polyethylene under various conditions of polymerization. The nascent polymer samples were examined by optical and electron microscopy, fuming nitric acid oxidation and differential scanning calorimetry. It was observed that the samples consisted of lamellar as well as fibrillar crystals. Examination of catalyst preparations by light-scattering photometry revealed the presence of a colloidal dispersion besides the soluble catalyst complex. It is proposed that the lamellar and fibrillar crystals have different origins. The lamellar crystals are formed by intramolecular crystallization of polymer chains generated from the soluble catalyst complex, whereas the fibrils are the product of intermolecular crystallization of polymer chains growing from adjacent active sites residing on the surface of the colloidal particles. The degree of chain extension in the fibrillar crystals is dependent on the conditions of polymerization.
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