Solution properties of poly(trimethylsiloxanotitanoxanes) (titanium oxide trimethylsilyloxides)

Abstract

To obtain more information on the structure of the polymeric hydrolysis products of Ti(OSiMe 3) 4, (the titanium oxide trimethylsilyloxides), measurements were made of the degrees of polymerization and hydrolysis, sedimentation, viscosity, specific volume, refractive index increment and turbidity of five hydrolysis products in cyclohexane solution. Refractive increments and turbidities were also measured for two products in carbon tetrachloride, benzene, chlorobenzene and bromobenzene. A self-consistent description of the properties of these polymers is based on repeating units containing a cube-shaped Ti 8O 12 structure. These units undergo condensation to give two types of chains having one and two bridging oxygens, respectively, between successive repeating units. Evidence for this model is obtained from the interdependence of degrees of polymerization and hydrolysis, from sedimentation, and from the dependence of turbidity on the refractive index of the solvent. Specific volumes calculated from the model agree well with experiment. Refractions for the Ti-1bO bonds in metalloxane chains, calculated from the refractive index increments, indicate that formation of longer chains causes an increase in refraction towards the value for TiO 2. The distribution of metalloxane links and the high polydispersity of the products presumably arise. from labile intermolecular condensation during hydrolysis.