High density polyethylene (HDPE) can be prepared from ethylene by

HDPE is prepared by co-ordination polymerization which occurs through the intermediate formation of co-ordination complexes. For example, ethylene first forms a coordination complex with the transition metal titanium by donating its $\mathrm{\pi }$-electrons. The $\mathrm{\pi }$ complex thus formed then reacts stepwise with a large number of ethylene molecules ultimately leading to the formation of a polymer. The polythene so obtained has high density (0.97 g/cm³) and higher m.pt. (403K) as compare to LDPE (density- 0.92 g/cm³ and m.pt. 384K)