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High-resolution proton nmr spectroscopy was used to investigate the solution polymerization of cyclic ethers. The concentrations of secondary and tertiary oxonium ions, the propagating species, have been determined from nmr spectra. In "living" systems, where chain transfer and terminations are negligible, the kinetic molecular weight can also be monitored during the polymerization process. Molecular weight maxima were found in systems where the formation of tertiary oxonium ion is slower than the propagation. This method is generally applicable to study the Cationic polymerization of cyclic ethers which do not have proton peaks interfering with the oxonium ion signals.

This article reviews tetrahydrofuran and oxetane polymers and polymerization. The physical and chemical properties of polytetrahydrofurans and polyoxetanes are discussed, as well as the polymerization mechanism, including initiation, propagation, termination, chain transfer, kinetics, and copolymerization to give block, graft, and star copolymers. The most important commercial product is poly(tetramethylene ether) glycol (PTMEG), sold under the trade names Terathane (Du Pont), PolyTHF (BASF), and Polymeg (QO Chemicals). The manufacture of PTMEG is described in some detail, including the most recent industrial processes. Storage and handling of PTMEG, as well as specifications and standards of commercial products, are given. Test methods used in the 1990s are referenced, such as hydroxyl number, polymer molecular weight, and molecular weight distribution. Health and safety factors are discussed, as well as the economic aspects of PTMEG production. Most important uses of PTMEG are in elastomeric polyurethanes and polyesters. The same type of information is given for oxetane polymers, although no oxetane polymer has found any practical application and is thus not available commercially as of 1995.

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