Write the free radical mechanism for the polymerization of ethene.


Chain initiation


The chain is initiated by free radicals, Ra, produced by the reaction between some of the ethene and the oxygen initiator.


Chain propagation


Each time a free radical hits an ethene molecule a new longer free radical is formed.


Ra + CH2 = CH2 RaCH2CH2


RaCH2CH2 + CH2 = CH2 RaCH2CH2CH2CH2


Chain termination


Eventually two free radicals hit each other producing a final molecule. The process stops here because no new free radicals are formed.


Ra(CH2)m + (CH2)n Ra Ra(CH2)m(CH2)nRa


Because chain termination is a random process, polyethene will be made up of chains of all sorts of different lengths.


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