JC Bevington Trans Faraday Soc 1955 51 1392 has shown that t

J.C. Bevington [Trans. Faraday Soc., 1955, 51, 1392] has shown that the fraction of radicals produced in the thermal decomposition of azobisisobutyronitrile that actually initiate the polymerization of styrene in benzene increases with increasing monomer concentration from a value of 0.17 at the lowest monomer concentration used, to an apparent limiting value of 0.65. Discuss possible reasons for the increase in this fraction as the monomer concentration is increased and explain why an efficiency of greater than 0.65 cannot be achieved.

Solution

The increase in fraction is because as the monomer concentration increases the collision between the monomer and the azobisisobutyronitrile also increases as a result of which there will be formation of more radical and hence concentration will increases but the efficiency cannot not be greater than 0.65 due to when there is more increase in monomer concentration the number of effective collision decrease and so is the efficiency.