Effect of catalytic system structure and conditions of oxidative polymerization of 2,6-dimethylphenol
on yield and molar mass of poly(phenylene oxide)
The activities of catalytic systems CuX2/L [where: X= Br¯, Cl¯, L = dibutylamine, N,N-dimethylbutylamine (DBA), N-methylaminopropyltrimetoxysilane,morpholine] in the oxidative polymerization of 2,6-dimethylphenol (2,6-DMP) topoly(phenylene oxide) (PPO) were compared. The effects of 2,6-DMP/Cu molarratio (500—750) in the most active CuBr2/dibutylamine system and the composition of toluene/hexane mixture as reaction medium on the PPO yield and molar mass were investigated. The CuBr2/DBA system (molar ratio 2,6-DMP/Cu =250) allowed to obtain the highest yield (90.4%) of PPO with the highest molar mass (67 900 g/mol). It has been found that in the presence of CuBr2/DBA during a dozen or so minutes after completing monomer dosing, low molecular weight product (5000 g/mol) was produced, after one hour polymer with molar mass typical for commercial species (56 800 g/mol) was produced, and further extending of the time did not significantly affect the molar mass of the product. The introduction of additional amine (N,N-dimethylbutylamine or N,N’-di-t-butylethylenediamine) enabled PPO synthesis with high yield and molar mass typical for that of commercial polymerat lower dibutylamine to Cu molar excess. The use of solvent/non-solventmixture turned out to be ineffective in the synthesis of PPO.