Synthesis of spirocyclosiloxanes for transparent copolymer thermosets

The use of multiple-ring cyclic molecules to generate crosslinked polymeric materials takes the advantages of small molecular precursors directly, but is retarded by the need of exact reactivity matching between different components. This problem was overcome by use of spirocyclosiloxanes, which were synthesized through the Piers–Rubinsztjan reaction. The two-level ring strain energies in these spirocyclosiloxanes help them accommodate a wide range of single-ring cyclic molecules to form highly transparent thermosets. The rich library of spirocyclosiloxanes, single-ring cyclic molecules, and catalysts makes this modular approach a promising method for the preparation of useful materials.