Effects of monomer length on α-olefins polymerization using a conventional Ziegler-Natta catalyst

alpha-Olefin monomers with different lengths from C-4 to C-10 were polymerized via a conventional Ziegler-Natta catalyst. It was found that activity of the catalyst decreases with increase in the monomer length as well as introduction of external donor. GPC results exhibited a steady decrease in molecular weight from poly1-butene to poly1-decene; however, PDI did not show a clear trend. Based on differential scanning calorimetry and X-ray diffraction analyses, poly1-butene and poly1-decene represented crystalline structure with one and two melting points, respectively, while poly1-hexene and poly1-octene showed amorphous nature. The content of isotactic pentads increased from poly1-butene to poly1-octene, with maximum value of mmmm = 76%, but decreased again in poly1-decene. Calculated Delta Ere-si values showed a peak by increasing monomer length which was in line with the experimental results for isotactic content.