The hydrolytic condensation of 1,3-dichloro-1,3-disila-1,3-diphenyl-2-oxaindane under neutral conditions produced alpha'omega-dihydroxy-1,3-disila-1,3-diphenyl-2-oxaindane (polymerization degree approximate to 4). The homofunctional condensation of alpha'omega-dihydroxy-1,3-disila-1,3-diphenyl-2-oxaindane in a toluene solution and in the presence of activated carbon was performed, and dihydroxy-containing oligomers with various degrees of condensation were obtained. Through the heterofunctional condensation of dihydroxy-containing oligomers with alpha'omega-dichlorodimethylsiloxanes in the presence of amines, corresponding block copolymers were obtained. Gel permeation chromatography, differential scanning calorimetry, thermomechanical analysis, thermogravimetry, and wide-angle roentgenography investigations were carried out. Differential scanning calorimetry and roentgenography studies of the block copolymers showed that their properties were determined by the ratio of the lengths of the flexible and linear poly(dimethylsiloxane) and rigid poly(1,3-disila-1,3-diphenyl-2-oxaindane) fragments in the macromolecular chain. At definite values of the lengths of the flexible and rigid fragments, a microheterogeneous structure was observed in the synthesized block copolymers.