ИСТИНА

Metal ions directed hydrolytic condensation of organotrialkoxysilanes, RSi(OR')3, leads to the formation of metallasiloxane molecules those contain only one type of cyclosiloxanolate fragments coordinated to a metal ions matrix. Mainly, the size of cyclic fragments depends on the type of metal ions used. The subsequent elimination of the metal centers by the reaction of the metallasiloxanes with triorganylchlorosilanes or dilute solutions of acids allows the formation of stereoregular cyclosiloxanes of different size in high yields. Thus a series of new cyclic compounds, [RSi(O)OSiMe2R']n (n = 3, 4, 6 , 8, 10, 12; R = Ph, Vi, Me, Et, Pr; R' = Me, Vi,CH2Cl, H) and [RSi(O)OH]n (R =Ph, n = 4, 6, 12; R = Me, n = 4) was produced. Many of these cyclics can not be synthesized by traditional reaction routes. A distinctive feature of their molecular structure is the presence of two different types of "covering groups" on both sides of the plane of the cycle creating a strong anisotropy of intermolecular interactions. This feature gives a whole series of unique properties to these cyclic materials. Many of them are mesomorphic compounds in spite of the fact that they do not contain classic mesogenic groups. The XRD, DSC, TGA investigations and the rheological properties of the cyclics obtained are presented.