Synopsisp-Chlorophenyldiazonium hexafluorophosphate is shown to be a convenient and effective catalyst for initiating the polymerization of tetrahydrofuran (THF) and other cyclic ethers. The polymerizations apparently proceed without any significant termination or transfer reactions (i.e., "living" polymers result), and materials of very high molecular weight can be obtained. A mobile monomer-polymer equilibrium for T H F was obtained during polymerization and equilibrium conversions were determined at a number of temperatures. The ceiling temperature derived from these data was 84OC., the heat of polymerization was -4.58 kcal./mole and the corresponding entropy change was -17.7 cal./"C.-mole. Hydrocarbons are suitable inert solvents for these polymerizations, but concentrated solutions must be used at ambient temperatures in order to stay above the required equilibrium monomer conceiitration and also to dissolve the catalyst which is insoluble in hydrocarbons. It was shown that acyclic ethers act as transfer agents in these polymerizations and that transfer with consequent reduction of molecular weight continues even after monomer-polymer equilibrium is reached. Cyclic ethers do not act as transfer agents but only copolymerize. Trimethyl orthoformate was shown to be a particularly effective transfer agent; it resulted in a polymer with methoxy endgroups and produced methyl formate as a by-product. The data obtained are consistent with a mechanism involving initiation by hydrogen abstraction and polymerization via tertiary oxonium ions associated with PFsgegenions. This gegenion is thought to be responsible for the "living" nature of the system.

No abstract

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.

No abstract

No abstract