We present a new method for epoxide polymerizations utilizing aluminum-based initiators, which leverage the chemical versatility of thiol compounds to control the polymer end group. The homo- and co-polymerization of various epoxides, such as epichlorohydrin and propylene oxide, demonstrate the flexibility of the initiators. Polymer molecular weight was controlled up to 100 kg/mol for the epoxides studied while maintaining relatively narrow dispersity (D < 1.4). We further characterized the kinetics of epoxide polymerizations through H-1 NMR spectroscopy and studied how the initiator structure impacted the kinetics. Finally, we employed our initiators to polymerize from thiol end-functionalized poly(methyl methacrylate) (PMMA) synthesized through reversible addition fragmentation chain transfer (RAFT) polymerization, which allows us to easily create block copolymers made from vinyl and epoxide monomers. Therefore, this new synthetic tool allows for the facile polymerization of epoxides into well-defined, functional, polyether materials.