Preparation
Low molecular weight polymers of tetrahydrofuran were introduced commercially in 1955. The polymers were intended for use in the preparation of
flexible polyurethane foams, being terminated by hydroxyl groups:
Although these polyethers produced good foams they were rather expensive
and were soon displaced by the cheaper propylene oxide-based polyethers.
However, these polymers of tetrahydrofuran (commonly called poly(oxytetramethylene)glycol) now find use in the preparation of polyamide, polyester and polyurethane thermoplastic elastomers.
Details of the manufacture of polytetrahydrofuran have not been disclosed.
Polymerization of tetrahydrofuran can be effected only by cationic initiators.
Combinations of metal halides with water are not effective but protic acids
(e.g. HCl04) and oxonium salts (e.g. (C2H5￡?3O+BF4-) are efficient initiators.
Polymerization occurs by a ring-opening mechanism involving a tertiary
oxonium ion, e.g.
