- A heptane-soluble polyisobutylene (PIB)-Cu(I) catalyst was synthesized in a heptane/ethanol latent biphasic solvent system. The addition of water to this initially homogeneous solution produced a biphasic solvent system that separates the PIB-Cu(I) complex from the reaction mixture as a heptane solution. This heptane solution can be used in reactions such as "click" chemistry where the PIB-Cu(I) catalyst is again separated from the reaction mixture as a heptane solution with the products of the reaction mixture being separated in the ethanol phase of the latent biphasic solvent system. This PIB-Cu(I) complex can also be used in an atom transfer radical polymerization (ATRP) of polystyrene. Using the differential solubilities of PIB and polystyrene in heptane, a PIB-complexed Cu(I) species can be separated and recycled for multiple uses in further polymerization reactions with good control over molecular weight and molecular weight distribution. Copyright 2007 American Chemical Society.