Abstract: A series of polydimethylsiloxane-polyphenolphlein tererpthalate multi-blook copo-lymer have been synthesized by using low temperature solution condensation tcchnicue.Structure characterization of the block copolymers by IR, ~1H-NMR,viscosimetry,TEM etc.indicates that copolymers with controlled siloxane content can be obtained in high mole-cular weight.The copolymers can be either elastomeric or rigid depending on the siloxane block length and its content.The copolymers show two-phase morphology, good mechanical properties, thermostability and film formability.