Solvent Selective Hydrogen–Deuterium Exchange on Saturated Polyolefins

A heterogeneous Pt–Re/SiO 2 catalyst was used to perform H–D exchange reactions on the linear saturated polyolefins poly(ethylene), poly(ethylene- alt -propylene), and isotactic poly(propylene) in the saturated hydrocarbon solvents decalin, decane, heptane, and isooctane. Exchange reactions using deuterium gas were selective toward the polymer in the case of linear and branched alkane solvents for poly(ethylene) and poly(ethylene- alt -propylene), whereas reactions conducted in decalin result in virtually no isotope exchange with the polymer. Essentially, no exchange occurred with poly(propylene) in either linear (decane) or branched (isooctane) solvents. In all cases, polymer backbone bonds were unperturbed, preserving the molecular weight distribution. These results suggest that competitive adsorption between the polymer and solvent plays a significant role in heterogeneous catalysis of polymers. Furthermore, this strategy provides a simple and efficient method for postsynthesis labeling selected polyolefins with deuterium, for example, for use in small-angle neutron scattering.