Hyperbranched poly(silyl ester)s were synthesized via the A(2) + B-4 route by the polycondensation reaction. The solid poly(silyl ester) was obtained by the reaction of di-tert-butyl adipate and 1,3-tetramethyl-1,3-bis-beta(methyl-dicholorosilyl)ethyl disiloxane. The oligomers with tert-butyl terminal groups were obtained via the A(2) + B-2 route by the reaction of 1,5-dichloro-1,1,5,5-tetramethyl-3,3-diphenyl-trisiloxane with excess amount of di-tert-butyl adipate. The viscous fluid and soft solid poly(silyl ester)s were obtained by the reaction of the oligomers as big monomers with 1,3-tetramethyl-1,3-bis-beta(methyl-dicholorosil)ethyl disiloxane. The polymers were characterized by H-1 NMR, IR, and UV spectroscopies, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The H-1 NMR and IR analysis proved the existence of the branched structures in the polymers. The glass transition temperatures (T-g's) of the viscous fluid and soft solid polymers were below room temperature. The T-g of the solid poly(silyl ester) was not found below room temperature but a temperature for the transition in the liquid crystalline phase was found at 42 degrees C. Thermal decomposition of the soft solid and solid poly(silyl ester)s started at about 130 degrees C and for the others it started at about 200 degrees C. The obtained hyper-branched polymers did not decompose completely at 700 degrees C. (c) 2006 Wiley Periodicals, Inc.