The cationic polymerization of epoxides determination of polymer structures by NMR spectroscopy

Although it is well established that the low temperature cationic polymerization of 3‐methylbutene‐1 and its homologs involves extensive rearrangement by hydride shifts, it has been shown by NMR spectroscopic analysis that the analogously constitute 1,3‐methyl‐1,2‐epoxybutane does not undergo a hydride shift when polymerized with boron trifluoride. Other epoxides of the type are shown also not to rearrange on cationic polymerization. The different behavior between the two systems is ascribed to differences in the types of carbonium ion intermediates involved in polymerization.