The formation of polyethylene involves the polymerization of ethylene C2H4 monomers. The mechanism of polymerization is called "coordination polymerization" or "Ziegler-Natta polymerization." This process uses a catalyst system, typically consisting of a transition metal compound e.g., titanium tetrachloride, TiCl4 and an organometallic compound e.g., triethylaluminum, Al C2H5 3 . The catalyst system plays a crucial role in the polymerization process by lowering the activation energy and increasing the reaction rate.Here's a detailed explanation of the process:1. Catalyst formation: The transition metal compound TiCl4 reacts with the organometallic compound Al C2H5 3 to form an active catalyst complex. The aluminum alkyl compound donates an alkyl group to the transition metal, resulting in a vacant site on the metal center.2. Monomer coordination: The ethylene monomer coordinates to the vacant site on the transition metal center of the catalyst complex. This coordination forms a metal-alkene bond.3. Insertion: The coordinated ethylene monomer inserts itself into the metal-carbon bond of the transition metal complex. This insertion step results in the elongation of the polymer chain by one monomer unit.4. Chain propagation: Steps 2 and 3 are repeated, with new ethylene monomers coordinating to the metal center and inserting into the metal-carbon bond. This process continues, leading to the growth of the polymer chain.5. Chain termination: The polymerization process is terminated by various mechanisms, such as chain transfer to the aluminum alkyl compound or reaction with impurities. The active polymer chain is removed from the metal center, and the catalyst complex returns to its initial state, ready to initiate another polymer chain.The overall reaction equation for the formation of polyethylene can be represented as:n C2H4 [-CH2-CH2-]nwhere n represents the number of ethylene monomer units in the polymer chain.In summary, the formation of polyethylene involves the coordination polymerization of ethylene monomers using a Ziegler-Natta catalyst system. The catalyst plays a crucial role in the process by activating the ethylene monomers and facilitating their insertion into the growing polymer chain.