Siloxane-type polymers chain ends

Reactive Homopolymers. Types of Reactions. In the typical ringopening polymerization mentioned previously see Preparation of Siloxane-Type Polymers), reactive hydroxyl groups are automatically placed at the ends of the chains (7, 13). Substitution reactions carried out on these chain ends can then be used to convert them into other functional groups. These functionalized polymers can undergo a variety of subsequent reactions (Table III). 

Polymers of this type are produced by either acid- or base-catalyzed polymerizations of cyclic siloxanes where trisubstituted siloxanes are used to end-cap the polymer chains and control the viscosity (VII). 

The manufacture of siHcone polymers via anionic polymerization is widely used in the siHcone industry. The anionic polymerization of cycHc siloxanes can be conducted in a single-batch reactor or in a continuously stirred reactor (94,95). The viscosity of the polymer and type of end groups are easily controUed by the amount of added water or triorganosUyl chain-terminating groups. 

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