Chain‐growth polycondensation of potassium 3‐cyano‐4‐fluorophenolate derivatives for well‐defined poly(arylene ether)s

Polycondensation normally proceeds in a step‐growth reaction manner to give polymers with a wide range of molecular weights. However, the polycondensation of potassium 2‐alkyl‐5‐cyano‐4‐fluorophenolate ( 1 ) proceeded at 150°C in a chain polymerization manner from initiator, 4‐fluoro‐4′‐trifluoromethyl benzophenone ( 2 ), to give aromatic polyethers having controlled molecular weights and low polydispersities ( M w / M n ⩽ 1.2). The resulting polycondensation of 1 had all of the characteristics of living polymerization and displayed a linear correlation between molecular weight and monomer conversion, maintaining low polydispersities. Sulfolane was a better solvent for chain‐growth polycondensation of 1 than other aprotic solvents. The polyether from 1 with a low polydispersity showed higher crystallinity than that with a broad molecular weight distribution, obtained by the conventional polycondensation of 1 without 2 .