SILICONE NETWORKS PREPARED VIA A LIVING PERCOLATION MECHANISM - POSTGELATION STRUCTURE FOR NETWORKS WITH A VARIETY OF JUNCTION FUNCTIONALITIES

Silicone networks were prepared by the trifluoromethanesulfonic-acid-catalyzed polymerization of octamethylcyclotetrasiloxane and an oligocyclosiloxane. The polymerization occurred by the random exchange of all siloxane bonds in the sol and the gel. Networks where the junctions were tri-, tetra-, penta-, hexa-, hepta-, or octafunctional were prepared. The final structure was modeled by a simple thermodynamic consideration of the ring-chain equilibrium involved. The sol was primarily composed of cyclic oligomers of dimethylsiloxane which were in equilibrium with the network. The composition of the various sized rings was analyzed to verify the structure assigned to the network. Equilibrium swelling studies were carried out which strongly supported the calculated structures. A correlation between the average functionality and cycle rank of nearly perfect lightly cross-linked networks is given.