Side-Loop Polymers Based on the Hydrosilylation of Polybutadiene

Hydrosilylation of hydride-terminated poly(dimethylsiloxane) with polybutadiene in dilute solution yielded polysiloxane side-loops on a hydrocarbon base, a novel polymer architecture. When the ratio of silane to olefin was increased, the inherent viscosity of solutions dropped drastically, and polymer properties changed from tough rubbers to tacky materials. The results are rationalized on the basis of diminishing availability of olefin sites as the reaction proceeds. When one end of a difunctional silane attaches to an olefin site and no other olefin sites are available nearby, molecular motion eventually brings a remote olefin site in the molecule into proximity. Hydrosilylation then results in permanent ring folding. Subsequent hydrosilylations can then result in a dendrimer-like globular molecule. Contact angle measurements of side-loop adducts show temporal stability, indicating that the tendency of poly(dimethylsiloxane) side chains to migrate to or away from the surface, depending on the medium, is circumvented by anchoring both ends.