Free Radical Polymerization Initiation step:The initiator reacts with the monomer to start the chain. heat benzoyl peroxide phenyl radicals styrene benzylic radical Copyright2005 Pearson Prentice Hall,Inc. Propagation step:Another molecule of monomer adds to the chain. many more styrene molecules H growing chain styrene elongated chain polystyrene n=about 100 to 10.000 Copyright2005 Pearson Prentice Hall,Inc. => Chapter 26 5Chapter 26 5 Free Radical Polymerization =>