Name: Introduction to Biodegradable Polymers
Uploaded: 2019-07-19
Duration: 6 min 16 s
Description: Polymers that decompose by the action of microorganisms are known as biodegradable polymers. Watch the video and learn about some of the important biodegrada...

Question

Write the free radical mechanism for the polymerisation of ethene.

Accepted Answer

Free radical mechanism for the polymerisation of ethene : Alkenes or ethene and their derivatives are polymerised in the presence of a free radical generating initiator (catalyst) like acetyl peroxide, benzoyl peroxide, tert-butyl peroxide, etc., e.g. polymerisation of ethene to polythene, involves heating or exposing to light, a mixture of ethene with a small amount of benzoyl peroxide (the initiator). This process follows three steps as given below:
Step I, Chain Initiating Step: Firstly, the phenyl radical is formed by homolytic cleavage of benzoyl peroxide. Then, phenyl radical is added to the double bond of ethene molecule (monomer) to form a new and a large free radical through homolysis.

Step II, Chain Propagating Step: The new large free radical thus formed in the chain initiating step reacts with another molecule of ethene to form further, larger sized radical. Thus, the repetition of this sequence with new and bigger radicals tends to carry the reaction forward.

Step lll, Chain Terminating Step: Ultimately, the growth of free radical chain may get terminated by reactions which consume these free radicals by combining them in different ways to form polythene.

Write the free radical mechanism for the polymerisation of ethene.

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