Allyl glycidyl ether, polymerized from potassium alkoxide/naphthalenide initiators under both neat and solution conditions was shown to be a highly controlled process. In both cases, molar masses (10-100 kg/mol) were determined by the reaction stoichiometry, and low polydispersity indices (1.05-1.33) could be obtained with a full understanding of the dominant side reaction, isomerization of the allyl side chain, being developed. The degree of isomerization of allyl to cis-prop-1-enyl ether groups (0-10% mol) was not correlated to the molar mass or polydispersity of the polymer but was dictated by the polymerization temperature. This allows the extent of isomerization to be reduced to essentially zero under either melt or solution conditions at polymerization temperatures of less than 40 degrees C. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4498-4504, 2011