Question

How "wastage reactions" can be minimized by taking into account such factors

1) radical stability, 2) radical 1/2 life, 3) monomer reactivity?

Answer 1

1) The initiator efficiency (f) is decreased by soilvent cage effect.If the radical stability is more ,it escapes from cage formation which prevents the wastage reactions.

2) The half life is the time needed for the initial concentration of initiator to decrease to half its initial value.it is related to the initiator decomposition rate constant K_d by

                             t_1/2 = ln2/ K_d

half life is more , intiator decomposition rate less, so less no. of radicals were formed.The radical concentration during polymerisation is not changed , but the initiator formed will be wasted by cage effect. As the radical half life is more ,it forms cage with the solvent molecules or other monomer molecules, so wastage is more.In order to minimise this the half life should be less.

3) The monomer reactivity increases with radical stability .Highly stable the radical ,minimise the waste reactions.