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 ¹H-NMR spectroscopy. A reaction mechanism is proposed to account for their formation.