The synthesis of polyethylene oxide PEO , also known as polyethylene glycol PEG , from ethylene oxide EO monomer is carried out through a process called anionic ring-opening polymerization. The mechanism of this polymerization reaction involves the following steps:1. Initiation: The reaction starts with the addition of an initiator, which is typically an alkoxide ion RO- or a metal alkoxide MOR . The initiator attacks the ethylene oxide monomer at the less hindered carbon atom, breaking the ring and forming a new alkoxide anion. This alkoxide anion is now attached to the ethylene oxide monomer, and the initiation step is complete.Initiator + Ethylene oxide RO-CH2CH2O-2. Propagation: The alkoxide anion formed in the initiation step acts as a nucleophile and attacks another ethylene oxide monomer at the less hindered carbon atom. This process breaks the ring, and the alkoxide anion is now attached to two ethylene oxide units. The propagation step continues with the alkoxide anion attacking more ethylene oxide monomers, resulting in the formation of a growing polymer chain.RO-CH2CH2O- + Ethylene oxide RO-CH2CH2O-CH2CH2O-3. Termination: The polymerization reaction can be terminated by adding a terminating agent, such as an alcohol ROH or an acid R-COOH . The terminating agent reacts with the alkoxide anion at the end of the growing polymer chain, forming a neutral polymer molecule.RO-CH2CH2O-CH2CH2O- + ROH RO-CH2CH2O-CH2CH2O-ORThe degree of polymerization and the molecular weight of the resulting polyethylene oxide can be controlled by adjusting the ratio of ethylene oxide monomer to the initiator. A higher monomer-to-initiator ratio will result in a higher molecular weight polymer.In summary, the synthesis of polyethylene oxide from ethylene oxide monomer occurs through anionic ring-opening polymerization, involving initiation, propagation, and termination steps. The polymerization reaction is controlled by the choice of initiator and the monomer-to-initiator ratio.