Method for preparing poly(tetramethylene ether) glycol

In a process for preparing poly(tetramethylene ether) glycol by polymerizing tetrahydrofuran using water or 1,4-butanediol as a chain terminator, the improvement comprising using as a catalyst a polymer of monoethylenically unsaturated monomers, the polymer being effectively free of functional groups which interfere with the polymerization and containing groups of the formula ##STR5## where

• represents the polymer chain or a segment thereof;
• D is hydrogen, an aliphatic or aromatic hydrocarbon radical of 1 to 10 carbon atoms, a halogen or a segment of the polymer chain;
• X and Y are hydrogen, an aliphatic or aromatic hydrocarbon radical of 1 to 10 carbon atoms, or fluorine, but at least one of X and Y must be fluorine;
• R is a linear or branched linking group having up to 40 carbon atoms in the principal chain;
• and
• Z is hydrogen, an aliphatic or aromatic hydrocarbon radical of 1 to 10 carbon atoms, or halogen.