Because of the increasing need for high-temperature resistant materials, like elastomers for applications in advanced technological areas (aerospace, defense, computer applications), a vast amount of research was developed in the area of inorganic-organic hybrid polymers. Organosiloxane polymers are one of the most important class of such materials due to their outstanding properties like thermal stability, low glass transition temperature, unusual surface properties, excellent gas permeability. But the classical polysiloxanes present the drawback of depolymerization in certain conditions (acid or base medium or high temperature). So, in order to try and avoid this possible depolymerization, a new class of polysiloxanes has been developed, mainly since the 1970s: the so-called "hybrid silicones", that are polysilalkylene siloxanes, fluorinated or not and polysilarylene siloxanes also fluorinated or not.
The elastomers prepared by crosslinking of these polymers present a very high thermal stability and a rather low temperature flexibility, and depending on the nature of their backbones or of their side chains, they may exhibit an excellent resistance to solvents or fuels.
This overview on Polysilalkylene or silarylene siloxanes fluorinated or not, so-called "Hybrid" silicones will present:
- the main synthetic routes to obtain these polymers.
*Synthesis of alpha,omega-bis silanol monomers (prepared either via an organometallic route or via hydrosilylation of alpha,omega-dienes) followed by polycondensation of these bis silanols
* Polyhydrosilylation of alpha,omega-dienes by alpha,omega-dihydrooligosiloxanes
- the properties of the different polymers.