ORGANIC INORGANIC HYBRID MATERIALS .2. COMPARED STRUCTURE OF POLYDIMETHYLSILOXANE AND HYDROGENATED POLYBUTADIENE BASED CERAMERS

Different ceramer networks were successfully prepared in bulk or in solution. High transparency was observed for all the samples based on hydrogenated polybutadiene (H-PBD) and polydimethylsiloxane (PDMS) oligomers. These materials are microphase-separated materials due to the thermodynamic incompatibility between the different constitutive units. A similar microstructure exists in both types of samples: silicate clusters (or more precisely, polysiloxane clusters) including the cross-link points are dispersed in the oligomer-rich phase. In the case of PDMS ceramers, the three types of constitutive units are immiscible, so the morphology of such materials may be described by a three-phase system including the soft phase, practically pure in PDMS, the silicate clusters, and an interfacial region containing the urethane-urea units. The structure of the polymer obliged this mixed phase to be between the soft and the hard segments. For H-PBD ceramers, the soft segments and the urethane-urea units are miscible, and a two-phase model may schematize the H-PBD ceramer structure. In every case, good correlation was observed between the clusters separation distances and the end-to-end distance of the oligomers. These schematic models are consistent with our experimental results: they explain the existence of a periodicity in the networks and the fact that the correlation distance increases with increasing oligomer length.