PHASE-TRANSFER CATALYZED POLYMERIZATION OF 4-BROMO-2,6-DIMETHYLPHENOL IN THE PRESENCE OF EITHER 2,4,6-TRIMETHYLPHENOL OR 4-TERT-BUTYL-2,6-DIMETHYLPHENOL

The synthesis of poly(2,6-dimethyl-1,4-phenylene oxide) with one 2,6-dimethylphenol chain end (PPO-OH) and with well-defined molecular weight by phase transfer catalyzed polymerization of 4-bromo-2,6-dimethylphenol (20) in the presence of either 2,4,6-trimethylphenol (1) or 4-t-butyl-2,6-dimethylphenol (1') as chain initiators is described. The range of controllable molecular weights and the mechanism of molecular weight control are discussed based on the differences between the reactivities of 20, 1, and 1' and of the corresponding reactive species. The PPO-OH synthesized from 20/1' has structural units derived from 1' attached only at the chain end. PPO-OH synthesized from 20/1 contains structural units derived from 1 both internally and at the chain ends. Structural units derived from side reactions were identified by H-1-NMR spectroscopy. A reaction mechanism is proposed to account for their formation.