Siloxane bond high energy

The chemical, physical, and thermal properties ana resistance to degradation of polysiloxanes is the result of the high energy (106 kcal/mol) and the relatively large amount of ionic character of the siloxane bond. The ionic character of the Si—O bond facilitates acid and base-catalyzed rearrangement and/or degradation reactions. Under inert conditions, highly purified polydiphenyl- and polydimethylsiloxanes are stable at 350 to 400 °C. 

Siloxane Bond Energy and Partially Ionic Character, Low intermo-lecular forces and high chain flexibility explain most of the physical behavior of PD MS in various environments. The hybrid organic-inorganic nature of PD MS has chemical consequences that are primarily due to two other key properties of the siloxane backbone its high bond energy and partially ionic character. For instance, these properties are clearly responsible for the substantial thermal stability of silicones. 

PDMS is the mainstay of the silicone industry, and the majority of its applications are related to its unusual surface properties. Most of these applications are not the result of surface behavior alone but come from desirable combinations of surface properties and other characteristics, such as resistance to weathering, high- and low-temperature serviceability, and high gas permeability. These applications are all a direct consequence of four fundamental structural properties of PDMS, namely (1) the low intermolecular forces between the methyl groups, (2) the unique flexibility of the siloxane backbone, (3) the high energy of the siloxane bond, and (4) the partially... 

Because of the high bond energy of the siloxane (Si—O) and phosphazene (P — N) groups, siloxane and phosphazene polymers are particularly stable at high temperatures. The Tt values of phosphazene halides increase from 183 K (NPFj) to 207 K (NPClj), to 265 K (NPBR. ... 

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