2. a. Write a short discussion on Ziegler-Natta polymerisation. Include in your discussion:

(i) A chemical equation for a Ziegler-Natta polymerisation reaction to form polyethylene.

(ii) An example of a heterogeneous catalyst/co-catalyst system. (iii) An example of a homogeneous catalyst/co-catalyst system.

(iv) A description of the mechanism of Ziegler-Natta polymerisation for the heterogeneous catalyst/co-catalyst system. Include chemical equations for steps in the Cossee-Arlman mechanism.