Cationic Polymerization Initiation steps:The catalyst protonates the monomer,starting the chain CH B+H,0: cH,→H-9 OH CH, CH H isobutylene initiated chain Copyright 2010 Pearson Prentice Hall.Inc Propagation step:Another molecule of monomer adds to the chain. tertiary carbocation CH CH CH H CH,H growing chain isobutylene elongated chain Copyright 2010 Pearson Prentice Hall,Inc. Strongly acidic catalysts are used to initiate cationic polymerization. ■ BFa is a particularly effective catalyst,requiring a trace of water or methanol as a co-catalyst.Intermediate must be a stable carbocation. Chapter 26 8 Chapter 26 8 Cationic Polymerization ▪ Strongly acidic catalysts are used to initiate cationic polymerization. ▪ BF3 is a particularly effective catalyst, requiring a trace of water or methanol as a co-catalyst. Intermediate must be a stable carbocation