Question

Isobutylene [H2C=C(CH3)2] cannot be readily polymerized by a free radical initiator. Are there good reason(s) for this or is it simply a matter of coincidence?

Answer 1

The carbon double bond is polymerized either free radical or ionic method but only isobutylene provide the carbonation stability for cation polymerization because series of para-substituent styrene the reactivity for substituent groups in cationic initiation is of the order of ring activation as
OCH3 > CH3 > H >Cl
Ortho substituents retard the addition regardless of whether they are activating or deactivating.