Process for prepolymers and products

Process for the preparation of linear terminally differentially electrophilically reactive prepolymer of tetramethylene oxide with 0 up to 50 mol% of comonomeric cationically polymerizable lactone or cyclic ether which comprises effecting polymerization of said tetramethylene oxide and said comonomeric lactone or cyclic ether at -20.degree. to 80.degree. C with initiator represented by the asymmetrical structure

• YO.sub.m SO.sub.2 R.sub.n Q
• wherein Q is a first radical which in anionic form is a nonterminating anion when 2 mol% of a dissolved salt of said anion is present during the polymerization of tetramethylene oxide containing 2 mole percent of ethylene oxide and 2 mol% of BF.sub.3 as polymerization initiator at 20.degree. C and said polymerization provides at least about 50 percent conversion of said monomers to polymer;
• Y is a second radical free from alkylatable groups, selected from alkyl, alkaryl, aryl, aralkyl and cycloalkyl and having the free valence on a carbon atom devoid of halogen atoms;
• n = 0 or 1;
• m = 0 or 1 and
• R is a divalent bridging radical comprising at least one oxytetramethylene radical, --(OR').sub.q -- where q is 1 to 300 and R' is alkylene of 2 to 10 carbon atoms at least one half of said alkylene groups being C.sub.4 H.sub.8.