A poly [4一(4’-octamethyltctrasiloxanyl) diphynylether] alternating eopolymer prepared by bulk polymerization,has been fraetionated by repeated precipitation method.All fractions together with unfractionated sample have been characterized by viseometry,dynamic osmometry,light scattering and GPC.After correction for polydispersity,a monodispersed [n]~M relationship has been obtained:For the copolymer in THF,The second virial coefficient A2 decreases as the mole-cular weight increases.The relationship is:We found that degradation oceured to some extent when the eopolymer was heated then kept for a few days in water.The results of investigation by UV and IR have shown that the chemical composition of the copolymer has not changed noticeably during deg-radation.