A series of s-tnazine-based hyperbranched polyethers (HBPE) have been synthesized to obtain thermostability but flexible polymers by an interfacial polycondensation of different diols as A(2) and cyanunc chloride as B-3 monomers using A(2) + B-3 approach in the presence of a phase transfer catalyst The polymerization reaction parameters are optimized, and the results indicate that the optimum conditions for the interfacial polycondensation are a 2.3 mole ratio of cyanuric chloride to diol using butanediol, benzyldimethylhexadecyl ammonium chloride as the catalyst, dichloromethane as the organic solvent, and a three-step procedure with keeping the reaction mixture at different low temperatures for 2h/2h/5h Other techniques such as high-temperature solution, one-step polycondensation, and transestenfication were also carried out to synthesize the HBPE but proved to be not suitable due to large number of side reactions The synthesized polymers were characterized by FTIR, H-1 NMR, and C-13 NMR spectroscopy, hydroxyl number determination, solution viscosity measurements, and GPC analysis The thermal behavior of the hyperbranched polymer was investigated by thermogravimetric analysis and differential scanning calorimetry All the results were compared with those from an analogous linear polyether, obtained from 2-methoxy-4,6-dichloro-s-triazine and butanediol by using the same polymerization technique. (C) 2010 Wiley Periodicals, Inc J Polym Sci Part A Polym Chem 48 3994-4004, 2010