Polyethylene is synthesized from ethylene monomers through a process called polymerization. There are two main types of polymerization processes used to synthesize polyethylene: free radical polymerization and coordination Ziegler-Natta polymerization. Here, I will describe the step-by-step mechanism for both processes.1. Free Radical Polymerization:Step 1: Initiation- A free radical initiator, such as a peroxide or an azo compound, is added to the ethylene monomer.- The initiator undergoes homolytic cleavage, producing two free radicals.- One of the free radicals reacts with an ethylene monomer, breaking the pi bond and forming a new single bond between the initiator radical and the ethylene monomer. This generates a new free radical on the ethylene monomer.Step 2: Propagation- The newly formed ethylene radical reacts with another ethylene monomer, breaking its pi bond and forming a new single bond between the two monomers. This generates another free radical on the newly added ethylene monomer.- This process continues, with the growing polymer chain reacting with more ethylene monomers, propagating the chain reaction.Step 3: Termination- The polymerization reaction is terminated when two free radicals react with each other, forming a stable covalent bond and ending the chain growth.- Termination can occur through various mechanisms, such as combination two growing chains reacting with each other or disproportionation transfer of a hydrogen atom from one chain to another .2. Coordination Ziegler-Natta Polymerization:Step 1: Formation of the catalyst- A transition metal catalyst, such as titanium tetrachloride TiCl4 , is combined with an organoaluminum compound, such as triethylaluminum Al C2H5 3 , to form a Ziegler-Natta catalyst.Step 2: Initiation- The ethylene monomer coordinates to the transition metal center of the catalyst, forming a metal-ethylene complex.Step 3: Propagation- The metal-ethylene complex reacts with another ethylene monomer, inserting the new monomer into the metal-carbon bond and forming a new metal-ethylene complex.- This process continues, with the growing polymer chain reacting with more ethylene monomers, propagating the chain reaction.Step 4: Termination- The polymerization reaction is terminated by adding a terminating agent, such as an alcohol or a hydrogen molecule, which reacts with the metal center and removes the polymer chain from the catalyst.In both processes, the result is a high molecular weight polyethylene polymer synthesized from ethylene monomers. The properties of the polyethylene, such as its density, crystallinity, and molecular weight, can be controlled by varying the reaction conditions and the choice of catalyst.