Three substituted unsaturated polycarbosilanes were prepared from the same parent using a two-step, one-pot ADMET polycondensation-nucleophilic substitution route. Condensation metathesis of di (4-pentenyl) dichlorosilane using Schrock's [Mo] catalyst produces a polymer backbone containing two reactive silicon-chlorine bonds per unit. Replacement of these bonds with stable alkyl moieties was performed using an excess of alkyllithium ...