Fluoride-initiated Anionic Ring-opening Polymerization: Mono- or Difunctional Polydimethylsiloxanes with Different Termini

The current paradigm in polymer chemistry increasingly involves controlled syntheses with better structural control and, consequently, products with narrow ranges of properties. Traditionally, silicone polymers are prepared under equilibrating conditions to give broad mixtures. The alternative, kinetically controlled ring opening polymerization at low temperature using organometallic initiators with promoters under inert atmospheres, can provide precise products. We report that fluoride, normally associated with desilylation reactions, may be productively used as a catalyst to prepare low dispersity polydimethylsiloxane polymers from D3 (hexamethylcyclotrisiloxane); solvency is key to the process. Polymerization at 0 °C in water-depleted, but not completely anhydrous, solutions leads to polymers with different groups at their α,ω-termini, including F and, optionally, a functional silane at the termini, respectively. The Si-F group can be converted to an Si-OH group using base to give difunctional linear silicones with two different functional termini.