Step II Chain propagation step The new free radical adds to another molecules of monomer to form a larger free radical.
Step III Chain termination step There are three ways of chain termination: Coupling reaction, disproportionation reaction, chain transfer reaction. One mode of termination of chain is shown as under:
( ii) Cationic polymerisation It involves formation of carbocation which are generated by Lewis acids( like BF3, AICI3, SnCI4, etc.) and protonic acids such as H2SO4, HF, etc.
Higher the stability of carbocation intermediate, more is the reactivity of monomers towards cationic addition polymerisation. It involves the following steps:
Step I. Initiation Step