Homopolymerization of Symmetrical Cyclosiloxanes

The reactivities of cyclotrisiloxanes and cyclotetrasiloxanes differ notably when the methyl groups are replaced by longer alkyl chains, or one or more functional groups are introduced on the cycle. The kinetics of ROP of cyclotrisiloxanes with 

BuLi + [2,1,1] as the initiator, the reactivity of V4 and V5 is almost the same as that of D3, while that of V3 is about 20-fold higher than that of D3. This order of reactivities V4 D3 D4 also holds for heterogeneous polymerizations catalyzed by ammonium hydroxide resins ]56]. 

In Table 3.2, the cychc trisiloxanes appear as two isomers, as and trans. The microstructure of the polymers bearing trifluoropropyl and phenyl substituents has been reviewed [118]. The rate of polymerization depends to a large extent on the nature of the substituent with, in general, the electron-withdrawing substituents increasing the reactivity, although the situation may be more complex [13]. 

Some fully functionalized monomers have also been studied recently. Hexa-n-alkylcyclotrisiloxanes with side chains ranging from butyl up to decyl have been 

The polymerization of monomers with mixed units (see Tables 3.3 and 3.4) leads to copolymers of functional siloxane and dimethylsUojane units. 

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