Instead of the conventional free radical polymerization of PS$,$ you decide to control the polymerization by use of a RAFT agent, DDMAT:

a$.$ Draw the reaction for the fragmentation of the RAFT agent.

b$.$ Draw two possible polymeric radicals with different chain ends fragmented from the RAFT agent.

c$.$ Describe how the RAFT agent enables the uniform growth of polystyrene chains without obvious termination. Write down a chemical equilibrium reaction including polystyrene chains and DDMAT, followed by proper explanation.

d$.$ For RAFT polymerizations, what could increase the possibility of undesirable side reactions and terminations?