Highly branched poly(arylene ether)s via oligomeric A₂ + B ₃ strategies

Branched poly(arylene ether)s were prepared in an oligomeric A₂ + B₃ polymerization of phenol endcapped telecholic poly(arylene ether sulfone) oligomers as A₂ and TFPPO as trifunctional monomer B ₃. The molar mass of the A₂ oligomer significantly influenced the onset of gelation and the DB. A high level of cyclization during polymerization of low molar mass A₂ oligomers (U₃ = 660 and U₆= 1200 g · mol^-1) led to a high conversion of functional groups in the absence of gelation, and the level of cyclization reactions in the polymerization decreased as the molar mass of the A₂ oligomer was increased. The pronounced steric effect in the polymerization of higher molar mass A₂ oligomers (U₈ = 1800 and U ₁₆ = 3400 g · mol^-1) resulted in low reactivity of the third aryl fluoride in the B₃ monomer. As a result, only slightly branched (U₈=1800 g · mol^-1) or nearly linear (U₁₆ = 3400 g · mol^-1) high molar mass products were obtained with higher molar mass A₂ oligomers. The branched polymers exhibited lower Mark-Houwink exponents and [η] relative to linear analogs, and differences between the branched polymers and linear analogs were less significantas the molar mass of the A₂ oligomers was increased due to a decrease in the overall DB.