The invention relates to polyethers of the formula I ##STR1## in which m is 0 or 1; n is an integer in the range from 3 to 100; R.sup.1, in the case where m is 0 or 1, is C.sub.1 -C.sub.36 alkyl or C.sub.7 -C.sub.36 aralkyl, each of which is unsubstituted or substituted by C.sub.5 -C.sub.8 cycloalkyl, is interrupted in the aliphatic part by C.sub.5 -C.sub.8 cycloalkylene or by oxygen or sulfur or --NR.sup.11 -- or is substituted in the aromatic part by 1 to 3 C.sub.1 -C.sub.4 alkyl and/or C.sub.1 -C.sub.4 alkoxy radicals; C.sub.3 -C.sub.36 alkenyl; C.sub.5 -C.sub.12 cycloalkyl which is unsubstituted or substituted by 1 to 4 C.sub.1 -C.sub.4 alkyl and/or C.sub.1 -C.sub.4 alkoxy radicals; C.sub.6 -C.sub.10 aryl which is unsubstituted or substituted by 1 to 4 C.sub.1 -C.sub.4 alkyl and/or C.sub.1 -C.sub. alkoxy radicals; and R.sup.1, in the case where m is 0, can alternatively be hydrogen; C.sub.1 -C.sub.36 alkoxy or C.sub.7 -C.sub. 36 aralkoxy, each of which is unsubstituted or substituted by C.sub.5 -C.sub.8 cycloalkyl, interrupted in the aliphatic part by C.sub.5 -C.sub.8 cycloalkylene or by oxygen or sulfur or --NR.sup.11 -- or is substituted in the aromatic part by 1 to 3 C.sub.1 -C.sub.4 alkyl and/or C.sub.1 -C.sub.4 alkoxy radicals; C.sub.3 -C.sub.36 alkenyloxy; C.sub.5 -C.sub.12 cycloalkoxy which is unsubstituted or substituted by 1 to 4 C.sub.1 -C.sub.4 alkyl and/or C.sub.1 -C.sub.4 alkoxy radicals; or C.sub.6 -C.sub.10 aryloxy which is unsubstituted or substituted by 1 to 4 C.sub.1 -C.sub.4 alkyl and/or C.sub.1 -C.sub.4 alkoxy radicals; R.sup.11 is C.sub.1 -C.sub.18 alkyl, C.sub.5 -C.sub.8 cycloalkyl, phenyl or C.sub.7 -C.sub.9 phenylalkyl; and X is an oxygen or sulfur atom.