AbstractWhen certain alkyl halides react with suitable inorganic salts in the presence of a heterocyclic monomer, polymerization ensues. Appropriate alkyl halides include allylic, tertiary, and benzylic chlorides, bromides, and possibly iodides. If the halide is a small organic molecule, a homopolymer is formed; if it is a polymer halide, a graft copolymer results. Soluble silver salts with counterions such as SO3CF3−, BF4−, PF6−, SbF6−, and ClO4− are most suitable, but LiPF6 and NaClO4 can also be used. So far, nine heterocycles have been polymerized by this method, e.g., tetrahydrofuran, 7‐oxabicyclo[2·2·1]heptane, propylene oxide, styrene oxide, dioxolane, trioxane, ε‐caprolactone, and thietane. To date, no effort has been made to optimize conditions for each monomer, but the preliminary data suggest that many of the expected side reactions are operative. Graft copolymers have been prepared from seven backbones: poly(vinyl chloride), neoprene, chlorinated EPDM, chlorobutyl rubber, bromobutyl rubber, chlorinated butadiene, and chlorinated butadiene‐styrene copolymer. In the most thoroughly examined cases with polytetrahydrofuran as the grafted copolymer and silver triflate as the inorganic salt, current data indicate that no unreacted backbone remains and no homopolymer forms. With some of the other monomers, homopolymer is formed in addition to graft during the grafting process.