Structural organization polyorganosiloxanes

An elastomer of the silicone family (see Silicones). It is a polyorganosiloxane, the backbone structure consisting of alternating silicone and oxygen atoms with organic groups, usually methyl, vinyl or phenyl radicals, attached to the silicon member. 

Summary The polycondensation of methyltrimethoxysilane in the presence of the surfactant benzethonium chloride shows the phenomenology of a polycondensation in microemulsion. These polyorganosiloxane micronetworks can be functionalized with azo groups which are capable of grafting reaction with vinylic monomers. The structure of the resulting core shell systems depends on the polarity of the organic solvent. In DMF moleculary dissolved star-like structures were observed. 

Access to the living cationic polymerization technique mentioned earlier has allowed the synthesis of a range of block copolymers, either phosphazene-phosphazene blocks, phosphazene-organic polymer blocks, or phosphazene-polyorganosiloxane blocks.Both di- and triblock copolymers have been produced, and a summary of these structures is shown in Scheme 7.7. 

Silicones are semi-inorganic polymers (polyorganosiloxanes) that may be fluid, elastomeric, or resinous, depending on the types or organic groups on the silicone atoms and the extent of cross-linkage between polymer chains. ° An example of silicone resin structure is seen in Figure 5.6. 

Among the poljrmers with inoi amc chains of the molecules, framed by organic groups, polyorganosiloxanes have been most studied. These high-molecular substances, the principal molecular chains of which are constructed of silicon and oxygen atoms, differ from organic polymers in their composition and the structure of the polymer molecules. In a consideration of thermal and thermooxidative destruction, these theoretical differences must be taken into consideration. 

According to the mechanism cited, it is easy to understand why polyethylsiloxane is more easily destroyed than polymethylsiloxane the -CH2- group of the ethyl radical and the silicon atom is oxidized more readily than the CH3-group. This reaction mechanism permits us to predict the thermal stability of polyorganosiloxanes on the basis of the structure of the organic radical or group at the silicon atom. 

The analysis of the effects of chemical structure both the siloxane backbone and the organic side groups of cyclolinear polyorganosiloxanes (POCS) on the phase transitions, the ability to form mesophase structures, the temperature range of mesophase existence and the structural evidence has been carried out. 

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